Physics 1A Final Exam
what is absoulute zero on celcius scale? Kelcvin
-273 C ; 0 K
Law
A general hypothesis or statement about the relationship of natural quantities that has been tested over and over again and has not been contradicted. Also known as a principle.
Convection
A means of heat transfer by movement of the heated substance itself, such as by currents in a fluid.
Entropy
A measure of disorder or randomness.
Temperature
A measure of how hot (or cold) something is; specifically, a measure of the average kinetic energy of the particles in an object.
force
A push or a pull
fluids
A substance that can flow and therefore take the shape of its container; a liquid or a gas
centrifugual means
"center fleeing" or "away from the center" it is an outward force
what does certipetal mean?
"center seeking" or "toward the center"
ideal efficiency equation
(hot temperature - cold temperature)/ (hot temperature)
if a blob of air initally 0 C expands adiabatcally while flowing upward adiabatically while flowing upward alongside a mountain a vertical distance of 1 km, what will its temperature be? When it gas risen 5 km
-10 C; -50
the law of conservation of energy states
Energy cannot be created or destroyed
Law of Conservation of Energy
Energy cannot be created or destroyed. It can be transformed from one form into another, but the total amount of energy never changes.
Radiation
Energy that is radiated or transmitted in the form of rays or waves or particles.
potential energy
Energy that is stored and held in readiness
heat
Energy that transfers from one object to another because of a temperature difference between the objects
The farther away the objects are from each other, the less force of attraction between them. Law can be expressed in
F ~ m1 m2 / d^2
law of conservation of momentum
In the absence of an external force, the momentum of a system remains unchanged
Who is the idea that gravity credited to?
Issac Newton
reaction force
One member of an action-reaction pair of forces that is equal in strength and opposite in direction to the action force that is its counterpart.
action force
One of the pair of forces described in Newton's third law
components
One of the vectors, often mutually perpendicular, whose sum is a resultant vector. Any resultant vector may be regarded as the combination of two or more components.
Describe the motion of a cannonball shot upward.
Pretend that here is no gravity and the cannonball follows a straight-line path. the cannonball continually falls beneath the imaginary line until it hits the ground. the vertical distance it falls beneath any point on the dashed line is the same vertical distance it would fall if it were dropped from rest and had been falling for the same time. This distance, is given by d=1/2dt^2
what scale is used in scientific research
SI scale of Kelvin the degrees are called kelvin 0 -> is the lowest possible temperature - absoulte zero zero on kelvin = 273 C
Terminal velocity
Terminal speed together with the direction of motion (down for falling objects)
What did Galileo argue?
That only when friction is present, is a force needed to keep an object moving
2. In 5 seconds a car moving in a straight line increases its speed from 50 km/h to 65 km/h, while a truck goes from rest to 15 km/h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vechical?
The Same, 3 km/hxs
At the instant a horizontally pointed cannon is fired, a cannnball held at the cannons side is released and drops to the ground. Which strikes the ground first, the one fired from the cannon or the one dropped?
The Same. They fall the same vertical distance wuth the same acceleration of g or 9.8 m/s^2 and therefore strike the ground at the same time.
Explain the term Absolute Zero in terms of temperature scale and kinetic energy of the substance.
The absolute zero is generally described as the "temperature at which a substance has no kinetic energy per particle (thermal) to give up." This temperature corresponds to 0 degrees Kelvin or -273 degrees Celcius. The absolute zero can be described in terms of the temperature scale. As the thermal motion of atoms increase, the temperature increases as well, and there really is no upper limit of the temperature. If you were to decrease the thermal motion of atoms in a substance, the temperature will drop. There is a definite limit on the other end of the temperature scale. At the top of the temperature scale, there is no upper limit, but on the bottom of the temperature scale, there is a definite limit. The term absolute zero can also be described in terms of the kinetic energy of the substance. As the thermal motion of atoms begins to approach zero, the kinetic energy approaches zero as well, and the temperature of the substance approaches a lower limit. At this limit, absolute zero, no more energy can be extracted from a substance and no further lowering of the temperature can occur. Overall, the absolute zero can be described in terms of the temperature scale and kinetic energy of the substance.
Newton's Second Law of Motion
The acceleration produced by a net force on an object is directly proportional to the net force, is in the same direction as the net force, and is inversely proportional to the mass of the object.
How does Bernoulli's Principle relate to lift?
The air travels faster over the top of the airfoil creating an area of low pressure. The airfoil moves into the area of low pressure.
if you place boiling water in two jugs, one black, one black like, what happens?
The black one will cool done much more quickly because it is a better emitter
net force
The combination of all forces acting on an object
Conduction
The direct transfer of heat from one substance to another substance that it is touching.
How does tangential speed relate to a giant rotating platform in an amusment park?
The faster the tangential speed, the faster it moves.
fulcrum
The fixed point around which a lever pivots
Do hypothesis need to be testable?
Yes. They are changed or abandoned if they are contradicted by experimental evidence
The speedometer of a car moving northward reads 60km/h. It passes another car that travels southward at 60 km/h. Do both cars have the same speed? Do they have the same velocity
Yes; No
if you were on the moon and dropped a hammer and a feather from the same elevation at the same time, would they strike the surface of the moon at the same time?
Yes; same weight, no air resistance
acceleration equation
a = f/m
What did Galileo discover about balls?
a ball rolling on a flat surface had constant velocity. He stated that if friction were absent it would keep rolling forever.
What is a scientific theory?
a body of knowledge and well-tested hypotheses about some aspect of the natrual world
Example of Greenhouse Effect
a car sitting in the sun on a hot day with its windows rolled up can get very hot inside, extremlely hotter than the outside air
what does a centripetal force play a main role in?
a centrifuge
A net force greater than zero causes...
a change in the motion of an object
fact
a close agreement by competent observers of a series of observations of the same phenomena
what kind of motion does a constant force produce on an object of fixed mass?
a constant force produces motion at a constant acceleration
machine
a device used to multiply forces or simply to change the direction of forces
free body diagram
a diagram showing all the forces acting on an object
Principle of flotation
a floating object displaces a weight of fluid equal to its own weight
When does impulse occur?
a force acts on an object over a period of time force over time causes acceleration acceleration is a change in velocity a change in velocity causes a change in momenutum a change in momentum is impulse
One joule of work is done when
a force of 1 N is exerted over a distance of 1 m
how does convection relate to archimendes's principle
because the warmer fluid is buoyed upward by denser surrounding fluid. this keeps things warm and heated
Water has __________ _________ capacity fro storing energy.
high heat
liquids exert a pressure in what directions within a liquid
equally in all directions within a liquid
When an object is at rest, with the net force on it being zero, we say the object is in a state of what?
equilibrium
heat transfer by radiation takes place form everything to everything
even in empty space
Why is water a good coolant or cooling agent?
high specific heat is use in cooling systems
the lift is greater for
higher speeds and larger wing areas.
at lower temperatures, the atoms and molecules of solids, liquids, and gases move less than at
higher temperatures thus they have less kinetic energy
a good absorber of radiant energy reflects very little radiant energy,
including visble lights, and thus appears dark
heat engine
is any device that changes internal energy into mechanical work
the useful work output of a machine
is less than the total work input
Temperature ________ a measure if the total kinetic energy of all molecules in a substance
is not
Characteristics of horizontal velocity
is not affected by gravity is a constant velocity the entire time an object is in the air. velocity = distance/ time distance = velocity x time
no machine can put out more energy than
is put into it.
If the speed of an object doubles, its kinetic energy
is quadrupled
what is the basic idea behind a heat engine?
is that mechanical work can be obtained only when heat flows from a high temperature to a low temperature. in heat engines only some of the heat can be transformed into work
what is the foundation of thermodynamics?
is the conservation of energy and the fact that heat flow from hot to cold.
linear speed
is the distance moved per unit of time
rotational speed (angular speed)
is the number of rotations per unit of timew
mass
is the quantity of matter in an object. the measure of the inerta that an object exhibts in response to any effort made to start it, stop it, or otherwise change its state of motion
Axis
is the straight line around which rotation takes place
Thermodynamics
is the study of heat and its transformation into mechanical energy.
the pressure the liquid exerts against the bottom of the container. . .
is the weight of the liquid divided by the area of the container bottom
wheneecer we change the pressire in one part of a fluid, this change
is transmitted to other parts.
how does the inverse square law apply to the force of gravity?
it applies to the weakening of gravity with distance
as air expands
it cools
iron is nearly eight times as dense as water, so when it is submerged,
it displaces 1/8 ton of water
when gravity is the only force acting on a projectile near earth, what happens to its horizontal component?
it does not change
when a gas adiabatically expands,
it does work on its surroundings and gives up internal energy
what happens to rising warm air?
it expands because there is less atmospheric pressure squeezing on it.
What is a difference between a ball falling straight down and one that is in a curved path?
it has a horizontal velocity
An object is in equilibrium when
it is at rest, with zero net force acting on it
what happens when radiant energy falls on other objects?
it is partly reflected and partly absorbed. The part that is absorbed increases the internal energy of the object
what does the value of G, tell us about the force of gravity?
it is very weak
how did newtons theory of gravitation confirm the Coperican theory of the solar system?
it proved that the Eartj was no longer considered the center of the universe, and that the Earth was the center of the universe. It became clear that the Eatyj and planets orbited the sun
When stone is placed in water, what happens to the water level
it rises, because the water is said to be displaced
The energy of an object enables
it to do work.
suppose a friend who hears about newtons third law says that you cant move a football by kicking it becasue the reaction force by the kicked ball would be equal and opposite to your kicking force. The net force would be zero, so no matter how hard you kick, the ball wont move! What do you say to your friend?
it will accelerate you kick acts on the ball no other force has been applied to the ball
if the surface is colder than its surroundings
it will be a net absorber and will become warmer
if the surface is hotter than its surroundings
it will be a net emitter and will cool
if the mass of 1-cubic-meter object is greater than 1.2 kg ...
it will fall to the ground
if the mass of 1-cubic-meter object is less than 1.2 kg ...
it will rise
If you wanted to create a barometer of water how tall does it need to be and why?
it would have to be 10.3 meters. this is because the density of mercury relative to water is 13.6 times as much. So a volume of 13.6 times as much water is required to provide the same weight as mercury in a tube
What does the amount of inertia an object has depend on?
it's mass, which is roughly the amount of material present in the object
if the surface emits more than it absorbs
its a net emitter
how much a liquid weighs and how much pressure it exerts depends on
its density.
when happens to the energy of an object, when it takes in or gives off heat?
its form of energy changes
if the momentum of an object changes what could have changed?
its mass, velcoty or both
Suppose you use a flame to add a certain quantity of heat to 1 liter of water, and the water temperature rises by two percent. if you add the same quantity of heat to 2 liters of water, by how much will the temperature rise?
its temperature will rise by 1 C, because there is 2 times as many molecules in 2 liters of water and each molecule recieves only half as much energy on average. so average kinetic energy and temperature increase by half as much.
When air resitance is present, a falling object accelerates only until it reaches...
its terminal speed
What does a vector represent?
its used to represent the magnitute and direction of a vector quantity. The lebgth of the arrow indicates the magnitude of the vector quantity. The direction of the arrow indicates the direction of the vector quantity.
When an object is at rest...
its weight is balanced by an equal and opposite support force
when the temperature of a substance is increased, its moleucles
jiggle faster and normally tend to move farther apart.
what is the unit of work?
joule or newton meter
SI unit for mass
kilogram
Mass is measured in?
kilograms
if an object is moving, then it is capable of doing work. It has energy of motion or...
kinetic energy
tempertaure is a measure only of the
kinetiic enrgy of translational motion
When the weight of a submerged object is equal to the buoyant force it will remain at
level
Bernoulli's principle explains
lifts planes fly
A graph with no acceleration and constant velocity
linear
How does a speed vs time graph look?
linear
aneroid baromters work without
liquids ad measure the postioin of a moable lid against a boc with low pressure inside.
object at low temperature emit ______ wavelengths.
long
at 500 C we can see what type of light and what wavelength at higher temperature it produces what light at 1200?
longest waves, red light yellow the eye is sensitive "white-hot
buoyancy is the apparent
loss of weight of an object immersed in a liquid
When a fluid flows with a high velocity, its pressure is __________, and where the velocity is low, the pressure is __________. A. high, low B. high, the same C. low, high D. low, the same
low, high
a stone is thrown into a deep lake. As it sinks deeper and deeper into the water, does the buoyant force on it increase, decrease, or remain unchanged?
remains unchanged
Mechancial energy is due to
the position of something (potential energy) or the movement of something (kinetic energy).
gravitational potential energy
the potential energy due to elevated positions
when the force is perpendicular to the surface area,
the pressure equals the force divided by the area over which it acts
Archimendes' principle
the principle that states that the buoyant force on an object in a fluid is an upward force equal to the weight of the volume of fluid that the object displaces
adiabatic
the process of compression or expansion of a gas so that no heat enters or leaves a system
Resolution
the process of resolving a vector into components
When a constant force moves an object in the direction of the force, the work done equals
the product of the force and the distance the object is moved.
work
the product of the force on an object and the sistance through which th object is moved (when force is consaynt and motion is in a straight line in the direction of the force); measured in joules
the specific heat capacity of any substance is defined as
the quantity of heat required to raise the temperature of a unit mass of the substance by 1 degree.
terrestrial radiation
the radiant energy emitted by Earth
Acceleration
the rate at which velociry changes
Power is the
the rate at which work is done
mechanical advantage
the ratio of the output force to the input force
Efficiency
the ratio of the useful work performed by a machine or in a process to the total energy expended or heat taken in. the ratio of useful work to total work input
a car accelerates along a road. Stickly speaking, what is the force that moves the car?
the road is pushing the car
Applied to heat engines, th second law states;
when work is done by a heat engine running between two temperatures, hot and cold, only some of the input heat at hot can be converted into work, and the rest is expelled as heat at cold.
How does a can relate to force?
when you swing a tin can in a circular path, there is no force pulling the can outward. Only the force from the string acts on the can pull the can inward. the outward force is on the strung not the can.
first law of thermodynamics
whenever heat is added to a system, it transforms to an equal amount of some other form of energy
for liquids of the same density, the pressure
will be greater at the bottom of the liquid
if the mass of 1-cubic-meter object is equal than 1.2 kg ...
will float in the middle
heat transfer by conduction takes place
within certain materials and from one material to another in contact
the quantity force x distance is called and the equation for what
work
Acceleration equation
change in velocity/time intervals
What does acceleration apply to?
changes in direction as well as changes in speed
Pascal's Principle
changes in pressure at any point in an enclosed fluid at rest are transmitted undiminished to all points in the fluid and act in all directions
eddy
changing, curling paths in turbulent flow of a fluid
if the surface absorbs more than it emits
net absorber
In the absense of what do objects not change their state of motion?
net force
what is acceleration directly proprtional to?
net force
if an object is accelerating, what does that mean?
net force acting on it
kinetic energy formula
net force x distance or Fd= 1/2mv^2
what does acceleration equal?
net force/ mass
acceleration equation
net force/ mass ; a=F/m
conservation of momentum equation
net momentum (before collision) = net momentum (after collision)
Is weight a scalar or vector quantity?Mass?
vector; scalar
barometer
An instrument that measures atmospheric pressure
When a weight lifter raises the barbell from the floor, is he doing work?
Yes.
work is a transfer of
from one object to another or from one form of energy to another
If you hold one end of a metal bar against a piece of ice, the end in your hand will soon become cold. Does cold flow from the ice to your hand?
heat flows from your hand to the ice. The metal is cold to touch because heat is transfering to the metal
An object more dense than the fluid in which it is immersed will...
sink
when the weight of a submerged object is greater than the buoyant force it will
sink
the greater the masses of an object
the greater the force attraction between them
The greater the impulse exerted on something
the greater will be the change in momentum
first law of thermodynamics
the heat added to a system is equal to the sum of the increasse in internal energy plus the external work done by the sytem.
if the force of air resistnce is the same for a falling baseball and a falling tennis ball, which will have the greater acceleration
the heavier baseball has the greayer net force and greater net force per mass.
does earth revolve or rotate?
Both! it revoles aorung the sun, and rotates around its axis.
on the international scale what temperature is when water freezes, and what temperature is it when water boils? What scale is this and what is the gap between the points called
0; 100 ; celsius , degrees
what is the relationship between calories and joules?
1 calories = 4.184 J
5285 meters x __________ = 5.285 km 892 grams = ___________ kg 0.60792 liters x ________ = 607.92 mL 6.2 km x __________ = 6200 m
1 km/1000 m 0.892 kg 1000 mL/1 L 1000 m/1 km
If twice as far, force of gravity will be
1/4 as weak
A piston in an airtight pump is withdrawn so that the volume of the air chamber is increased 5 times. What is the change in pressure?
1/5
radiant energy
Any energy, including heat, light, and X rays, that is transmitted by radiation. It occurs in the form of electromagnetic waves.
What two things enter into every case where work is done?
Application of a force the movement of something by that force
who discovered the relationship between the buoyancy and displaced liquid?
Archimendes
the greater the masses...
.. the greater the force
What net force do objects of balanced force have? Acceleration? Describe their forces?
0 N ; 0 m/s^2 ; forces are equal in magnitude and oppoosite in direction
what is the ideal effeicncy of an engine if both its hot reservoir and exhaust are the same temperature - say 400 K.
0 percent
How many significant figures? 0.003 mL
1
what is the relationship between joules and Calorie?
1 Calorie = 4184 Joules
Step of the Scientific Method
1) Recognize a problem 2) Make an educated guess - hypothesis 3) Predict the consequences of the hypothesis 4) Perform experiments to test predictions 5) Formulate the simplest general rule that organized the three main ingredients; hypothesis, prediction, and experimental outcome.
Understanding the greenhouse effect requires knowing about two concepts
1. All things radiate, and the wavelength if radiation depends on the temperature of the object emitting radiation 2. the transparency of things such as air and glass depends on the wavelength of radiation. Air is transparent to both infrared (long) waves and visible (short) waves, unless the air contains excess carbon dioxide and water vapor, in which case it is opaque to infared. glass is transparent to visible light waves, but is opaque to infared
What does added energy do to objects in a system?
1. increases the internal energy of the system if it remains in the system 2. does external work if it leaves the system
how much mass of air is in a cubic meter of air at 20 C have?
1.21 kg
how much density of air is in a cubic meter at 0 C? 10 C? 20 C? 30?
1.29, 1.25, 1.21, 1.16
if 10 J of energy is added to a system that does no external work, by how much will the internal energy of that system by raised?
10 J
What is the accerlation of an object under conditions where air resistance is neglible?
10 m/s
Does an object in free fall have a consatnt acceleration?
10 m/s^2
what is the ideal efficiency of a machine having a hot reservoir of 400 K and a cold reservoir at absolute zero, 0 K?
100 %
kilocalorie (kcal)
1000 calories the quantity of heat required to raise 1kilogram of water by 1-degree centigrade
any 1-cubic meter object in air is buoyed up with a force of ...
12 N
2. If a cheetah can maintain a constant speed of 25 m/s, it will cover 25 meter every second. At this rate, how far will it travel in 10 seconds? In 1 minute?
250 m 1500 m
How many significant figures? 4200 m
2
1 kg = ? lbs
2.2 lbs
the boy on the tower in figure 3.17 throws a ball a disatcne of 20 m. at what speed is the ball thrown?
20 m/s
How many significant figures? 1.06 x 10-3 km
3
How many significant figures? 15.92 g
4
What would the speedometer reading on the falling rock showsn in figure 2.5 be 4.5 seconds after it drops from rest? How about 8 seconds after it is dropped? 15 seconds?
45 m/s, 80m/s, 150 m/s
1. Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/h. What is its acceleration?
5 km/hxs
An apple drops from a tree and hits the ground in one second. What is its speed upon striking the ground? What is its average speed during the one second? How high above ground was he apple when it first dropped.
5 m
imagine a giant dry-cleaners garment bag full of air at a temperature of -10 C floating like a balloon with a string hanging from a 6 km above the ground. If you were able to yank it suddenly to the ground, what would its approximate temperature be?
50 C
How many significant figures? 1390.00 cm
6
if 10 J of energy is added to a system that does 4 J of extrnal work, by how much will the internal energy of that system be raised?
6 J. we see that the first law that 10 J - 4 J = 6J
G (gravitational constant)
6.7 x 10^-11
how long is a mercury barometer?
76 cm
Suppose a car with a miracle engine is able to convert into work 100% of the energy relased when gasoline burns (40 million joules per liter). If the air drag and overall friction forces on the car traveling at highway seed are 500 N, what is the upper limit in disatnce per liter of gasoline the car could cover at highway speed?
80 km
when the brakes of a motorcycle traveling 60 km/h becomes locked, how much further will the motorcycle skid than if it travels at 20 km/h?
9 times
What is the acceleration due to gravity?
9.8 m/s^2
1 kg = ? N
9.8 newtons
about how many kilograms of air occupy a classroom that has a 200 sq m floor area and a 4 meter high ceiling
960 kg
Standing in front of a fire in a fireplace will warm you by A. convection. B. conduction. C. radiation.
A
There are two blocks sitting at room temperature. One is a black wooden block and the other a black metal block. A piece of ice is placed on each block. The ice melts faster on the metal block. The reason for this is _________________________. A. the metal block is a better conductor of heat B. The reason cannot be explained. C. the wooden block is warmer than the metal block D. the metal block is a better insulator of heat
A
Water resists a change in temperature because A. it has a high specific heat capacity. B. it is less dense at 0° Celsius. C. it vaporizes at 100° Celsius. D. it has a low specific heat capacity.
A
inelastic collison
A collision in which the colliding objects become distorted, generate heat and possibly stick together. A collision in which the colliding objects become distorted and/or generate heat during the collision are stuck together
0.0982 m = __________ m 75,639 g = __________ g 3.9 x 102 s = __________ s 4.687 x 10-4 km = __________ km 3.68 x 10-8 mL = __________ mL
A. 9.8 x 10^-2 m B. 7.5639 x 10^4 g C. 390 s D. 0.0004687 km E. 0.0000000368 mL
Which of the following involves great amounts of human passion, talent, and intelligence? a. literature b. science c. music d. art
All
calorie
Amount of energy needed to raise temperature 1 gram of water 1 degree C
Vector
An arrow whose length represents the magnitude of a quantity and whose direction represents the direction of the quantity.
Hypothesis
An educated guess
a ball is rolled across a counter top and rolls slowly to a stop. How would Aristotle interpret this beavior? How would Galilo interpret it? How would you interpret it?
Aristotle: it seeks it natrual state of rest Galileo: friction between ball and table overcomes the balls natrual tendancy to continue rolling
During the span of the second time intercal in table 2.2, the object begins at 10m/s and ends at 20m/s. What is the average speed of the object during this 1-second interval? what is its acceleration?
Average speed: 15 m/s Acceleration: 10 m/s^2
Archimedes' principle states that an object is buoyed up by a force equal to the A. density of air. B. weight of air it displaces. C. weight of the object.
B
If you mix one liter of water at 60° C with one liter at 30° C, what will the temperature of the water be when it reaches thermal equilibrium? A. 55° C B. 45° C C. 40° C D. 30° C
B
What two variables affect the acceleration of a ball? A. mass and weight of ball B. mass of the ball and net force placed on the ball C. weight and volume of ball D. density and volume of ball
B
Where is the pressure greatest in a lake 10 meters deep? A. The pressure is the same at any point in the lake. B. At the bottom of the lake C. 5 meters below the surface D. 1 meter below the surface
B
Why is it called tangential speed?
Because the direction of motion is always tangent to the circle.
why doesnt the sun fall around the planets?
Because the sun id more massive than the planets
Why don't action and reaction forces cancel each other out?
Because they are forces on different objects
The acceleration due to gravity on the moon is 1/6 that on Earth. What would a 55 kg astronaut weigh on the moon? A. 54 N B. 9 N C. 90 N D. 110 N
C
What are the two ways you car can accelerate?
Change in speed or Change in direction
changing velocity
Changing speed, direction, or both
constant velocity
Constant speed and constant direction
If you put pennies in the back of a toy dump truck so that the total mass (pennies + truck) is three times the mass of the empty truck, and you push it as hard as you did when it was empty, the truck's forward acceleration will. A. decrease by a factor of 9. B. increase by a factor of 9. C. increase by a factor of 3. D. decrease by a factor of 3.
D
Judy plays tug-of-war with Dana. If Judy pulls the rope, the reaction force is A. Judy pulling on Dana. B.the rope pulling on Dana. C. Dana pulling on the rope. D. the rope pulling on Judy
D
Krista walks at a constant speed to her car and suddenly realizes she forgot her phone. She runs back to the house to get it. Her motion could be described as having A. positive velocity toward the car and negative velocity back to the house. B. positive acceleration toward the car and negative speed back to the house. C. positive acceleration toward the car and negative acceleration back to the house. D. negative velocity toward the car and positive acceleration back to the house.
D
When a ship moves from salt water to fresh water, it floats A. at the same level. B.None of the choices are correct. C.higher. D. lower
D
What keeps molecules on Earth?
Earths gravity, without it they wouldnt
What tempertaure scale is used in the US and what is its freezing and boiling temperatures?
Farhenhite scale; 32 is freezing and 212 is boiling
air resistance
Fluid friction acting on an object moving through the air
normal force
For an object resting on a horizontal surface, the upward force that balances the weight of the object; also called the support force.
the proprtionallity form of law of universal gravitation can be expressed as an exact equation when the constant of propotionallity ...
G, universal gravitational constant is introduced
magnitude
Greatness of size, strength, or importance
Newton and the moon
He knew that if the moon did not fall, it would move off in a straight line and leave its orbit. he believed it was falling around Earth. Thus, the moon falls benaeth the straight line that it would follo if no force acted on it. he hypothesized that a projectile circling Earth under the attraction of gravity.
Speed
How fast something is moving; the path distance moved per time. The magnitude of the velocity vector. The rate at which distance is covered.
power
How fast work is done
Carnot efficiency
Ideal maximum percentage of input energy that can be converted to work in a heat engine.
,Can accelration be considered an increase or decrease in speed?
It can be both an increase and decrease.
What happens to an object when a net force acts on it?
Its acceleration increases
when the speed of a fluid increases
Its pressure decreases
energy is measured in
Joules
Kinetic energy equation
KE=1/2mv^2
Newton's First Law is also called what?
Law of Inertia
deceleration or negative acceleration
Means the velocity of a body is decreasing
is it more effiecent to paint a heating radiator black or silver?
Most of the heat provided by a heating radiator is accomplished by convection, so the color is not really important. But for more efficency, the radiators should be painted black so that he contribution by radiation is increased.
free fall
Motion under the influence of gravitational force only
linear motion
Movement in a straight line.
SI unit of force
Newton
what did newton deduce about the force of attraction between objects of different distances
Newton deduced that the force decreases as the square of the distance between the centers of mass of the objects. the farther away the objects are from each other, the less force of attraction between them
Are mass and volume related?
No
When a weight lifter is holding a barbell over his head, is he doing any work on the barbell?
No he is not. The barbell is not moving by the force he exerts, so he does no work on the barebell
Do action-reaction forces cancel?
No they do not
Do action-reaction forces cancel?
No, because they are acting on different objects
is it correct to say that the reason an object resists change and persists in its state of motion is that it has inertia?
No, we dont know the reason why objects persist in their motion when notion acts on them, but we call this property inertia.
When a dish falls, will the impulse be less if it lands on a carpet than if it lands on a hard floor?
No. The impulse would be the same for either surface becasue the same momentum changes occur for each. It is the force that is less for the impulse on the carpet because of the greater time for momentum change.
Consider what would happen if you suspended a 10-N object midway along a very tight, horizontally stretched guitar strings. Is it possible for the string to remain horizontal without a slight sag at the point of suspension?
No. if the 10-N load is to hang in equilibrium, there must be a supporting 10-N upward resultant. the tension in each huiltar string must form a parallelogram with a vertically upward resultant. For a slight sag, the sides of the parallelogram are very, very long and tension force is very large. To approach no sag is to approach an infinite tension.
Boyle's Law
P1V1=P2V2 A principle that describes the relationship between the pressure and volume of a gas at constant temperature
what is pressure measured in?
Pascals (Pa)
impulse
Product of force and time interval during which the force acts. Impulse equals momentum change.
suppose that an airplane normally flying at 80 km/h encounters wind at a right angle to its forward motion - a cross wind. Will the airplane fly faster or slower than 80 km/h?
Quicker
what will happen to a lighter person when someone of a large mass runs into her?
Same force on different mass objects causes different acceleration, thus she will move much further since she has a smaller mass.
What is the difference between science and technology?
Science deals with theoretical questions, while technology deals with practical problems.
velocity
Speed in a given direction
Pascal principle and the pistons
Suppose you have a tube on the right side wider and use a piston of larger area. The piston on the left has an area of 1 sq cm, and the piston on the right has an area of 50 sq cm. Suppose there is a 1-N load on the left, then an addiotnal pressure of 1 newton per sq cm is transmitted throughout the liquid and up against the large piston. The addiotnal pressure of 1 N/cm^2 is exerted aginst every sqaure centimeter of the larger piston. Since there are 50 sq cm, the total extra force exerted on the larger piston is 50N. Thus, the larger piston will support a 50-N load
the massiveness of the cement block plays an important role in this demonstration. Which provides more safety, a les massive block or a more massice one?
The greater the mass of the block, the smaller the acceleration of the block and bed of nails toward the person. Much of the force goes into breking the block.
Jason hits a baseball off a tee toward right field. The ball has a horizontal velocity of 10 m/s and lands 5 meters from the tee. What is the height of the tee? Show your work, including formula(s) and units.
The height of the ball will be 1.22 meters, you can figure this out by using the equation to find the height. To find time; distance/ speed = time ; 5/10 = .50 seconds H = ½g x t² H = 1/2 (9.8) x .50² H = 1.22 meters
Why should students be aware of significant figures in calculations?
The main purpose of sig figs and rounding rules is to ensure that calculated values do not over (or under-represent) the limitations of the equipment used to make the measurements.
What is the relationship between mass and inertia?
The more mass an object has, the greater its inertia and the more force it takes to change its state of motion.
When objects collide in the absence of external forces, what happens to the momentum?
The net mometum of both objects
What happens when a diver opens its parachute?
The parachute increases the diver's air resistance, so now gravity has an equal but opposite force. These forces are now balanced and there is no longer any acceleration. The diver will now slow down to a constant speed. This constant speed is called terminal velocity
if the force of gravity between the suna nd planets suddenly disapprear, what types of path would the planets follow?
The planets would move in straight lines at constantspeed - at constant velocity
Newton's Law of Cooling
The rate of loss of heat from an object is proportional to the temperature difference between the object and its surroundings.
State the second law of thermodynamics, in terms of heat transfer, and describe a scenario in which you have observed this law in action.
The second law of thermodynamics, in terms of heat transfer, states that "heat will never itself flow from a cold object to a hot object." It states that the direction of heat flow during any natural process. An example of a scenario that I observed in action is during birthday parties when you light a candle. When you take a lighter and light the candle, the heat from the lighter transfers to the unlit candle. The heat transfers from the hot object to the cold object, thus providing heat to the unlit candle and lightening it up. If the second law of thermodynamics didn't apply here, any heat in the unlit candle would transfer to the lit candle, adding more heat to that, but that isn't the case, due to the second law. Another example is when a heating pad is used to relieve any body pain. The heating pad has heat in it, and when placed on a body part, the heat transfers from the pad, hot object, to your body, the cold object. This shows the second law of thermodynamics in action. But if the second law didn't apply here, the heat from your body would transfer from your body to the pad, making you colder and the pad hotter. But if you have used a heating pad before, you know that isn't the case.
thermal equilibrium
The state of two or more objects or substances in thermal contact when they have reached a common temperature, and no heat flows between them
absoulute zero
The temperature at which molecular energy is at a minimum the temperature called at which no more energy can be removed from matter
Why are theories sometimes modified?
They are modified because new evidence is brought in.
touch a piece of metal and a piece of wood in your immeediate vicinity. Which one feels colder? Which one is really colder?
They both should have the same temperature The metal feels colder.
What makes metals good conductors?
They have free flowing, loose electrons
if a 300 grams brick weight 3 N in air, and submerged 2 N of water, the bouyant force on the submerged brick will also equal 2 N. The brick seems to weigh less under water why?
This weight is 3 N and the buoyant force is 2 N, so the 1N is its weight in watr]er
If a forklift is replaced with a new forklift that has twice the power, how much greater a load can it lift in the same amount of time? If it lifts the same load, how much faster can it operate?
Twice as much load twice as fast
what are the types of lever?
Types 1: fulcrum is in the middle Type 2: fulcrum is in between the fulcrum and input force Type 3: the fulcrum is at one end and the load is at the other
Momenta combine by:
Vector rules
Work equation
W=Fd work= force x distance
Impulse = Change in Momentum
What is impulse
Why is it easier to lift a boulder that is submerged in water?
When the boulder is submerged, the water exerts an upward force that is opposite in direction to gravity.
we know that if a fish makes itself more dense, it will sink; if it makes itself less dense, it will rise. In terms of buoyant force, why is this so?
When the fish increases its density, by decreasing its volume, it displaces less water, so the buoyant force decreases. When the fish decreases its density by expanding, it displaced more water, and the buoyant force increases.
How does centrifugal force related to a rotating can?
When the string breaks the can goes off in a tangential straight-line path because no force acts on it.
Newton's Third Law of Motion
Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
Are mass and weight proportional?
Yes
Are weight and mass proportinal?
Yes
Is physics the most basic of all sciences?
Yes
The text states that a 1-kg bag of nails weighs 9.8 N at Earths surface. Does 1 kg of yogurt also weigh 9.8 N?
Yes
can the pivot point or fulcrium be close to the load?
Yes
is accceleration directly proprtional to net force?
Yes
Does a 2 kg iron block have twice as much inertia as a 1-kilogram block of iron? Twice as much mass? Twice as much volume? Twice as much weight, when weighed in the same location
Yes to all; twice as much atoms
Is projecile motion is always parabloic?
Yes, if you neglect air resistance
describe a mercury barometer
a glass tube longer than 76 cm and closed at one end, is filled with mercury and tipped upside down in a dish of mercury. The mercury in the tube runs out of the submerged open bottom until the level falls to about 76 cm. The empty space trapped above, except for some mercury vapor, is a vacuum. The vertical height of the mercury column remains constant even when the tube is tilted unless the top of the tube is less than 76 cm above the level in the dish. in which case the mercury completely fills the tube.
a relatively small amout of water absorbs
a great deal of heat for a correspondingly small temperature rise
Pulley
a kind of lever that can be used to change the direction of a force can multiply forces
If an object has a large mass, it may or may not have
a large volume
Insulator
a material that does not conduct heat well; a material through which charges cannot easily flow
Weight
a measure of the gravitational force acting on an object
Volume
a measure of the space occupied by the object measured by cubic centimeters, liters
Scientific Method
a method that is extremely effective in gaining, organizing, and applying new knowledge.
an interaction between two things prodcues what
a pair of forces
How is linear speed related to a merry-go-round?
a point on an outer edge of a merry-go-round or turntable moves greater distance in one complete roation than a point near the circle. The linear speed is greater on the outer edge of a rotating object than it is closer to the axis.
scalar quantity
a quantity that can be described by magnitude only and has no direction
vector quantity
a quantity that requires both magnitude and direction for a complete description
lever
a simple machine that consists of a bar that pivots at a fixed point called a fulcrum
How does a lever work?
a small input force exerted through a large distance will produce a larger output force over a correspondibgly short distance. In this way, a lever can multiply forces.
Theory
a synthesis of a large body of information that encompasses well-tested and verified hypotheses about certain aspects of the natural world
Celsius scale
a temperature scale that defines the freezing point of water as 0 degrees and the boiling point of water as 100 degrees
a completely submerged object displaces
a volume of liquid equal to its own volume
A completely submerged object always displace
a volume of liquid equal to its own volume.
a child ono a sled (total weight 500 N) is pulled up a 10-m slope that elevates her a vertical distance of 1 m. a. What is the theoretical mechanical advantage of the slope? b. if the slope is without friction, and she has pulled up the slope at a constant speed, what will be the tension in the rope? c. considering the practical case where friction is present m suppose the tension in the rope was actually 100 N. HWayt is the actual mechanical advantage of the slope? what would the efficiency be?
a. 10 b. 50 N, with no friction, ideal mechanical advantage, and actual mechanical advantage would be the same, 10. So the rope tension, or input force, will be 1/10 the weight being raised, 500 N. c. the actual mechanical advantage is (weight bring raised)/(input force) = (500N)/(100 N) = 5. The efficiency would be 0.5 or 50 %, since (actual mechanical advantage)/(theoretical mechanical advantage) = 5/10 = 0.5. The efficiency can also be obtained from the ration (useful work)/(work input)
a. how much work is done on a 100-N boulder when you lift it 1m? b. What power is expended if you lift the boulder a distance of 1 m in a time of 1 s c. what is the gravitational potential energy of the boulder in the lifted position
a. 100 J b. 100 W c. it depends, relative to its starting position, the boulders PE 100J
The speedometer in every car also has an odometer that records the distance traveled. a. If the odometer reads zero at the beginning of a trip and 35 km a half hour later, what is the average speed? b. Would it be possible to attain this average speed and never exceed a reading of 70 km/h on the speedometer?
a. 70 km/h b. No
Which of these is a scientific hypothesis? a. Atoms are the smallest particles b. The universe is surrounded by a second universe, the existence of which cannot be detected by scientists. c. Albert Einstein was the greatest physicist of the twentieth century
a. Atoms are the smallest particles It is capable of being proven
air exerts pressure on everything; the pressure at sea level is
about 100 kPa
Earths atmosphere is an ocean of air extending...
about 30 km above Earths surface, with thinner air extending even higher.
the force of gravity is an unbalanced force, so it causes objects to ...
accelerate
Different masses equal different
acceleration
Force causes...
acceleration
acceleration equation
acceleration ( along a straight line) = change in speed/time interval
Newton's second law equation
acceleration is inversly proptional to the net force/ mass
instantaneous speed equation
acceleration x elapsed time = instantaneous speed
you must have energy to
accomplish work
two interacting forces are called
action force and reaction force
when you step on a bathroom scale, the downwaes force supplied by your feet and the upward force supplied by the floor compress a calibrated spring. The compression of the spring gives your weight. In effect, the scale measures the floors support force. What will each scale read if you stand on two scales with your weight divided equally between them? What happends if you stand with more weight on one foot than the other?
add up to weight
air can be changed by
adding or subtracting heat or by changing the pressure of the air
When working, we lift a load...
against Earths gravity
adiabatic process in the atmosphere occurs in large masses of air called? Where do changes un pressure and temperature occur
air blobs, on the edges
you can stick your hand into a hot pizza over for several seconds without harm, whereas you'd never touch the metal inside surfaces for even a second. why?
air is a poor conductor, so the rate at which the heat flows from the hot air to your relatively cool hans , is low. But the metak us a good conductor of heat, and a lot of heat in a short period of time is conducted into your hand when thermal contact is made
Convection occurs in
all fluids
How do you calculate significant figues?
all non-zeros are significant all zeros between non-zeros are significant trailing zeros with decimals are signifcant trailing zeros are not significant leading zeros are not significant (its easier to know how much if you out it in scienctific notation and check)
if heat is added to a system that does no external work, then the
amount of heat added will be equal to the increase in the internal energy of the system
centrifugal force
an apparent outward force on a rotating or revolving body. it is frictitous in the sense that it is not part of an interaction but is due to the tendency of a moving body to move in a straight line path.
An objet tends to remain at constant speed in a straight line (constant velocity) until...
an external force acts on it
if the elevation of the flowing liquid does not change, then
an increase in speed means a decrease in pressure.
impulse is greater when...
an object bounces
Newton's first law of motion
an object in motion will remain in motion unless acted upon by another force every object continues in a state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted on it
Archimedes' principle (for air)
an object in the air is buoyed up with a force equal to the weight of the displaced air
satellite
an object that falls around Earth or some other body rather than falling into it
as thermal motion approaches zero, the kinetic energy of atoms approaches zero
and the temperature approaches a low limit
centripetal force
any force that causes an object to follow a circular path
in the first law of thermodynamics, the system is
any group of atoms, molecules, particles or objects
what is pressure?
application of force over an area
the moon and other objects in orbit around Earth...
are actually falling toward Earth but have a great enough tangential velocity to avoid hitting Earth.
objects moving at constant velocity..
are also at equilibrium
good reflectors
are poor absorbers
What are scientific methods?
are procedures for anwsering questuibs about the world by testing educated guesses and formulating general rules.
the wings of faster-moving aircraft
are relatively small
the lever, pulley, and inclined plane
are simple machines
Each obbject is then emitting as much
as its obsorbing
the absorbed energy may also increase the rotation of molecules, increase the internal vibration within molecules, or stretch intermolecular bonds and be stored
as potential energy
What was Copernicus's theory on the moving Earth?
assumed Earth moved around the sun
Boyle's law states that
at constant temperature, the pressure times the volume of an enclosed has is constant, if one increased, another decreases.
a scuba diver 10.3 meters deep breates cmpressed air. If she holds her breath while returning to the surface, by how much does the volume of her lungs tend to increase.
atmospheric pressure can support a column of water 10.3 m high, so the pressure in water due to the weight of the water alone equals the atmospheric pressure at a depth of 10.3. taking the pressure and the waters surface into account, the total pressure at this depth is twice atmospheric pressure. Unfortunately, the scuba diver's lungs will inflate to twice their normal size if she holds her breath while rising to the surface. This is fatal.
Simple barometers meausre
atmospheric pressure in terms of how high a column of mercury in a closed tube can be support by atmospheric pressure
impulse is the...
average force x by the time during ehich it acts
What are two types of speed?
average speed and instantaneous speed
what is temeperature directly proportinal to?
average transitional kinetic energy of molecules within an ideal gas
A kitten knocks a toy off a bookshelf and it hits the floor in 0.5 s. How high is the shelf from the floor? A. 3.1 m B. 1.2 m C. 4.9 m D. 2.5 m
b
Which of the following is not a vector quantity? A. velocity B. time C. momentum D. force
b
you can hold your fingers beside the candle flame without harm, but not above the flame. Why?
because heat travels upward by air convection. since air is a poor conductir, very little heat travels sideways.
why is it called potential energy?
because in the stored state it has the potential for doing work
why do metals feel colder when you touch them?
because it is a better conducter of; heat is easily moving from your warmer hand into your cooler hand.
why doesnt wood feel cold when you touch it?
because it is a poor conductor. When you took a piece of it, your hand doesnt sense that it is toucing something colder, becasuse little heat is transfering out of your hand.
Suppose oone glider is at rest and is loaded so that it has three times the mass of the moving glider. Again, the gliders stick together when they collide. Desrcib etheir motion after the collision.
before collison, the net momentum equals the momentum of the unloaded, moving glider. After the collison, the net momentum is the same as before, but now the gliders are stuck together and moving as a single unit. the mass if the stuck together gliders is four times that of the unloaded glider. Thus, the postcollison velocity of the stuck-together gliders is one-fourth of the unloaded gliders velocity before collison. This velocity is the same direction as before, since the direction as well as the amount of momentum is conserved.
Suppose both gliders have the same mass and stick together when they collide. The gliders move toward each other at equal speeds. Describe their motion after the collision
before the collision, the gliders have equal and opposite momenta because their equal masses are moving in opposite directions at the same speed. the net momentum of the two gliders as a system is zero. Since momentum is conserved, their net momentum turn after sticking together must also be zero. they slam into a dead halt.
A single pulley, type 1 lever
behaves like a type 1 lever. the axis of the pulley acts like a fulcrum and both lever distances are equal so the pulley does not multiply force. it just changes the direction of the applied force mechanical advantage is 1
Two balloons are inflated to the same size, on with air and the other with helium. Which balloon experiences the greater buoyant force? Why does the air-filled balloon sink and the helium-filled balloon float?
both are buoyed up with the same force because they displace the same weight of air. the air filled is heavier than the buoyany force that acts on i. The hellium filled is lighter than the buoyant force that acts on it.
What did Newton deduce about a cannonball and moon?
both have a component of veloity parallel to Earths surface. This sideways or tangential velcoity is sufficent enough to ensure nearly circular mtoion around earth. if there is no air resistance, it will continue falling around the Earth.
what forces act on an object in a liquid?
buoyancy and weight
The weight of the displaced water is the
buoyant force
According to Archimedes' principle, an immersed object is
buoyed up by a force equal to the wieght of the weight of fluid it displaces
How is gravity simulated?
by centrifugual force.
What was newton puzzled about?
by the fact that the moon does not folloe a straight-line path, but instead circles the earth. he knew that the circular motion is accelerates motion, which requires a force. But didnt know what the force was. He figured that the moon was falling for the same reason tha apple was fallling, they are both pulled by gravity.
the impulse exerted on something is equal to...
change in momentum it produces
How can an object accelerate?
change in speed, direction, or both
Acceleration = _______________ divided by __________
change in velocity / time
what is the most commonly used unit for heat?
calorie
how can adiabatic changes of volume occur?
can be achieved by performing the process rapidly so that heat has little time to enter or leave, or by thermally insulating a system from its surroundings
at absoulute zero, no more energy
can be extracted from a sybstance and no further loweing of its temperature is possible.
The force of gravity between two objects:
can be found by multiplying their masses, multiplying it by the square distance and multiplying by the constant G
chaging heat completely into work
can never occur
conduction of heat
can take place within materials and between materials that are in direct contact
Examples of something that rotates
carnival ride and skater route
an object moving in a circle is acted on by a
centripetal force
elastic collision
collision in which colliding objects rebound without lasting deformation or heat generation is not stuck together
conduction is explained by
collisions between molecules and atonmsm and the actions of loosely bound electrons
the density of air can be doubled by
compressing the air to half its volume
how can the equalization of temperature occur?
conduction, convertion and radiation
metals are good
conductors
When friction is negligible does a ball move at a constant or unconstant velocity?
constant
for a projectile, when no horizontal force is acting on the projectile i s the horizontal velocity unconstant or constant?
constant
how does convection relate to winds?
convection currents stir the atmospere and produces winds. the uneven absorbtion of heat causes uneven heating of air near the surface and creates convection currents.
winds result from
convection currents that stir the atmosphere
all work you fo in overcoming friction is completely
converted into heat
if you keep the temperature difference small, the rate of
cooling will be correspondingly low
the pressure at equal distances below a surface is
equal and the same
it takes four times the work to _____ the speed
double
free fall; how far equation
d=1/2gt^2
good absorbers appear
dark
what causes an increase in air pressure?
decrease volume of the container of air add more aur molecules increase the temoerature of gas
Density in the atmosphere ________ with altitude
decreases
Why was Galileo important?
demolished the notion that a force is necesary to keep an object moving
what happedns to the centrifugal and centripetal force when you double distance from the axis?
doubles
Velocity differs from speed in that velocity is speed with_______.
direction
Acceleration like velocity is...
directional
Force and acceleration are
directly proportional
Entropy is a measure of
disorder in a system. Whenever energy freely transforms from one form to another, the direction of transformation is toward of greater disorder
organized energy degenerates into
disorganized energy
perturbation
disturbance
centrifual force is a ______ of rotation
effect
work is required to...
elevate objects against Earths gravity
action and reaction froce are
equal but opposite in direction
At any point within a liquid, the forces that produce pressure are exerted
equally in all directions
every surface, hot or cold, both absorbs and
emits radiant energy
good absorbers of radiant energy are good
emitters
Does energy change?
energy can change from one form to another, without net loss or net gain.
mechanical energy
energy due to the position of something or the movement of something
kinetic energy
energy of motion
thermal energy
energy resulting from heat flow
matter contains __________ in several forms, but it does not contain _______.
energy; heat
disorder increases;
entropy increases
According to Newtons law of universal gravitation,
everything pulls on everything elsee with a force that depends on the masses of the objects and the distances between their center of mass
If you wish to change the momentum of an object,
exert an impulse on it
the total pressure at any given point in a liquid is the pressure
exerted by the liquid plus the pressure of the air above it.
matter tends to _________ when heated and _____ when cooled.
expand ; contract
a common therometer measures temperature by showing the. . .
expansion and contraction of a liwuid in a glass tube.
an adiabatic process is one usually
expansion or compression, wherein no heat enters or leaves a system
a brick mason wishes to mark the back of the building at the exact height of the bricks already laid at the front of the building. How can he measure the same height using only a garden hose and water?
extend garden hose that is open at both ends from the front to the back of the house. it will fill up with water until the water reaches the height of the bricks, Since water seeks its own level, the level will be the same
second law of thermodynamics
heat does not spontaneously flow from a cold object to a hot object. No machine can be completely effcient in converting energy to work; some input energy is dissipated as heat. All sysytemms tend to become more and more disorder as time goes by
stimulated gravity
feels like gravity they are acustomed to
wood is a better insualtor than glass. Yet fiberglass is commonly ised to insulate wwooden buildings. Why?
fiberglass is a good insulatoe, because of the air that is trapped within its fiber
what sources give a sensation of heat and what do they emit
fireplace, lamp, sun. they emit infrared radiation and visible light.
When the weight of a submerged object is less than the bouyant force it will
float.
an object less dense than the fluid in which it is immersed...
floats
weight = mass x acceleration due to gravity
formula for weight
weight = mg
formula for weight
convection occurs in all
fluid
a floating objet displaces a weight of
fluid equal to its own
projectiles
follow a curved path
the product of the pressure and volume
for a given mass of gas is constant as long as the temperture doesnt change
What happens when air is enclosed
for example inside a tire, molecules behave like ping pong balls, that are perpetually moving and banging against the wall. their impact on this wall produces a jittery force that appears to our coarse senses as a steady push. this pushing force averaged over a unit of area provides the pressure of the enclosed air
Bernoullis principle holds only
for steady flow, in which the flow follows stream lines
different substance have different capcities
for storing internal energy
What is the cause of acceleration?
force
support force
force that completely balances the weight of an object at rest
examples of centripetal forces
force that holds the occupants safely in a rotating carnival ride is a cener directed force. Without it the motion of the occupants would be along a straight line- they would not revolve gravitational force directed toward the center of Earth holds the moon in an almmost circular orbit aoround Earth
Impulse equation
force x time interval
an object moving twice as fast takes
four times as much work to stop
different frame of refrence from a lady bug
from a stationary frame of reference outside the whirling can, we see there is no centrifugal force acting on the ladybug inside the whirling can. However, we do see centripetal force acting in the can, producing a circular motion. Thus, from an outside stationary frame of reference, the only force acting on the ladybug is the centripetal force exerted by the bottom of the can on the ladybugs feet In the rotating frame of reference, both centripetal force (supplied by the can) and centrifugal force (act on the ladybug.
What symbol is used to represent acceleration due to gravity?
g
Good Absorbers are also...
good emitters
a poor conductor is a ....
good insulator
air is a really
good insulator
porous materials with a lot of small holes are
good insulators
how does heat engines relate to reserviors?
heat flows from a high-temperature reservoir to low temperature reservoirs. Every heat engine will (1) absorb heat from a reservoir of higher temperature increasing its internal energy, (2) covert some of this energy into mechanical work, and (3) expel the remaining energy as exhaust.
second law of thermodynamics
heat will never spontaneously flow from a cold object to a hot object
Types of potential energy
gravitational, elastic, chemical
newton did not discover gravity, but discovered that
gravity is universal
Greater force yields
greater acceleration
The greater the force the greater the velocity, and hence
greater its change in momentum
for liquids of different densities, the one with the greatest will have
greater pressure
Greater Inertia...
greater tendency at rest
What net force do objects of unbalanced force have? Acceleration? Describe their forces?
greater than zero N, greater than 0 acceleration ; forces are not equal
the greater the masses of ...
greater the force of attraction between them
how did newton try to prove his theory?
he reasoned that the mass of the moon should not affect this fall, and that it should only relate to their respective distances from Earths center if the distance of fall for the moon and apple are correct in proportion, then the hypothesis that Earths gravity reachs the moon is true
Sadi Carnot found what?
he showed that the upper fraction of heat that can be converted into useful work, even under idea conditions, dpedns on the tempertature difference beteeen the hot and cold sink.
matter does not contain _______, but contains _____________.
heat ; internal energy
first law of thermodynamics states
heat added = increase in internal energy + external work done by the system
Thermodynamic is the study of
heat and work
the rate of cooling of an object depends on
how much hotter the object is than the surroundings
What is the difference between theory and hypothesis?
hypothesis is a prediction based on the results of an expirement, while a theory has a lot of data to support it. You cant prove a theory, but you can prove a hypothesis.
steam engine relation to added heat
if a given supply of heat is added to a supplied steam engine, some of the heat increases the internal energy of the system and the rest is transfered into mechanical work
if a good absorber of radiant energy were a poor emitter, how would its temperature compare with its surroundings?
if a good absorber were not also a good emitter, there would be a net absorbtion of radiant energy and the temperature of a good absorber would remain higher than the temperatures surrounding
if two identifical balls rolled against each other what would happen?
if they hit one another going at the same speed, they will recoil from the hit and move in the opposite direction. each ball will move in reverse the same amount of distance at the same speed. This is becasue the balls had equal masses and we know that equal deoces on equal masses casue equal acceleration.
what other way can we increase the internal energy of a system? Give example
if we set "heat added" to zero, we will see that changes in internal energy are equal to the work done on or by the system ex., if work is done on a system by compressing it, the internal energy increase, and therefore have an increase in temperature without any heat input. but if we do work on the system by expanding it, the internal energy decrease, and we therefore have a cooler system with a decrease in temperature
How does a passanger in a car relate to a centripetal force?
if you are a passenger in a car that suddenly stops short, and you are not wearing your seatbelt, you will pitch forward toward the dashboard. When this happens you say it is because of the absense of a force, which the seatbelt usually provides. if you are in a car that rounds a sharp corner to the left, you tend to pitch outward against the right door. This is because there is no centripetal force force holding you in circular motion.
how does conduction relate to a metal rod over flame?
if you hold one end of an iron rod in a flame, the rod will become too hot to hold. This heat is transferred through the metal by conduction. In the iron rod, the flame causes the atoms at the heated end to vibrate more rapidly. These atoms vibrate against neighboring atoms, which in turn do the same. Most importantly, the free electrons that can drift through the metal are mad to jostle and transfer energy by colliding with atoms and other free electrons within the rod
How can gravity be simulated
if you increease the radial distance of the roatating body, you increase the centifugual and centripetal accerlertaion. Or if you increase the size o the circumfrence, it will increase the forceof simulated gravity
decribe an example of convection
if you take a test tube and hold it with tongs and plane an ice cube and water in it and place it overheat, you will see that the ice floats at the surface. You will see that the ice will melt quickly. heat gets to the top by convection, for the hot water rises to the surface, carrying its energy with it to the ice.
how does a florist greenhouse relate to greenhouse effect.
in a florists greenhouse, heating is mainly due to the ability of glass to prevent convection currents from mixing the cooler outside air with the warmer inside air. So the greenhouse effect plays a bigger role in global warming than it does in warming of greenhouse.
Rate
in physics, how fast something happens, or how much something changes per unit of time; a change in a quantity divided by the time it takes for the change to occur
if the system does external work, then
increase in internal energy will be correspondingly less
What causes a substance to expand
increase in temperature spreads the molecules out farther
how do you increase the momentum of a ball?
increase the impact force and increase the impact time
for any natrual process entropy
increases
the pressure at the walls of the pipe decreases when the speed of water
increases
neaely all matter _______ when its temperature increases and ______ when its emperature decreases.s
increases ; contracts
absorbed energy that increases transitional speed of molecules is responsible for
increases in temperature
if the volume of a gas decreases, what happens to pressure? How are the two related?
increases; inversely
Mass is a measure of
inertia
the more mass the more
inertia
Momentum
inertia in motion; the mass of an object multiplied by its velocity
What is work input and work output equation
input (force x distance) = output (force x distance)
For a given force, acceleration and mass are
inversely proportional to each other
What casues friction?
irregularities in the surface
Characteristics of vertical velocity
is affected by gravity is not constant calculated by using the free-fall equation distance = 1/2 at^2
poor consuctors, such as wood, cork, and most liuids are good
insulators
mass and acceleration are
inversely proportional
low-speed gliders have very
large wings relative to the size of the fuselage
More mass yields
less acceleration
absoulte zero is the
lowest possible temperature taht a substance may have; where molecules of a substance have minimal kinetic energy
What quantities do vectors have?
magnitude direction
centripetal force is the force required to
maintain circular motion
The lines of fluid in a streamline are closer togetehr in
narrower regions where the flow is faster and pressure is less.
kilograms
mass
what two things does gravity depends on? which has a larger effect?
mass and distance; distance because it is squared
What does acceleration depend on?
mass and force
to quantify heat, we must specificy the
mass and kind of substance
What does kinetic energy depend on?
mass and speed
the momentum is the product of its...
mass and velocity
Difference between mass and weight
mass is the quantity of matter in an object and weight is mass x gravity Mass is how much matter an object has and weight is how strong gravity pulls on the matter of a mass.
what is acceleration inversly proprtional to?
mass of object
momentum equation
mass x velocity mass x speed momenum = mv
conducters
materials that conduct heat well
specific ______ require specific quantities of _______ to raise the temperature of a given mass of the material by a specificed number of degrees.
materials; heat
What were the types of motion according to Aristotle?
natrual motion (finding natrual resting position) and violent motion (result of forces that pushed or pulled)
how can the second law be states as the state of order
natrual systems tend to proceed toward a state of greater disorder.
an objetc will equal density to the density of the fluid in which it is immersed will
neither sink nor float; remain at leverl
the amount of heat transfered can be determined by
measuring the temperature change of a known mass of water that absorbs heat.
What is the best conductor?
metal; silver, copper
a force sustained for a long period of time produces...
more change in momentum than the same force applied briefly
nonlinear motion
motion along a curved path
streamlines
motion of a fluid in a steady flow.
heat transfer by convection takes place by the
movement of heated material itself.
what is the pressure within a tornado like?
much less
the hydraluic press, based on Pascals principle,
multiplies force.
a machine is a device for
multiplying force or changing the direction of force
the resulatant of the tension forces, or the diagonall of the paralleogram
must be equal and oposite to the loan supported.
Is there an upper limit to temperature? lower limit?
no ; yes, its absoulute zero.
when an object moves in a circle, there is...
no force pushing the object outward from the circle.
what does the second law tell us about heat engines?
no heat engine can convert all he heat input into mechanical energy output.
Two forces act on a book resting on a table: its weight and the support force from the table. Does a force of friction act as well?
no not unless the book tends to slide
a perfect absorber reflects
no radiant eneergy and appears perflectly black
At the center of a rotating platform, right at its axis, do you have a tangential speed? Rotational speed?
no tangential speed you rotational speed
since a hot cup of tea loses heat more rapidly than a lukewarm cup of tea, would it be correct to say that a hot cup of tea will cool to room temperature before a lukewarm cup of tea will.
no, because although the rate of cooling is greater for the hot cup, it has further to cool in order to reach thermal equilibrium. The extra time is equal to the time it takes to cool to the initial temperature of the lukewarm cup of tea. Cool rate and cooling time are not the same
Suppose that an apple at the top of a tree is pulled by Earth's gravity with a force of 1 N. If the tree were twice as tall, would the force of gravity on the apple be only 1/4 as strong? Explain you anwser.
no, because the twice-as-tall apple tree is not twice as far from Earths center. the taller tree would have to have a height equal to the radius of Earth before the weight of the apple would be reduced to 1/4
Does a stick of dynamite contain force? Explain.
no, force is not something an object has. Force is an interaction between one thing and another. it can have the capability of exerting a force on another object, but it cannot possess force as a thing itself
In attempting to do the demonstration shown in figure 5.8, would it be wise to begin with a few nails and work upward to more nails?
no, there would be greater pressure which would cause harm
Where is the tension greater, a pair of vertical or nonvertical springs?
nonvertical springs and depends on theri angle from the vertical
In the abssense of force, what happens to an object?
object at rest remain at rest and objects in motion continue in motion
efficiency can be expressed at the ratio
of actual mechanical advantage to theoretical mechanical advantage
carnots equatoin states the upper limit
of efficency for all heat engines
Mass in the measure of what?
of inertia in an object
Energy can be transformed from
one form to another
what is the overriding concept of the second law of thermodynamics
only some heat input can be converted into work, even without friction
How does a distance vs time graph look?
parabloic
A graph of a free falling object with acceleration
parabolic
interaction
part of mutual action between one thing and another
If a boxer is able to make the contact time five times longer by "riding" with the punch, how much will the force of the punch impact be reduced?
reduced by 5 times as much
A good absorber of radiant energy
refects very little radiant energy
What is physics
physics is how stuff works
is there more pressure at the bottom of a bathtub of water 30 cm deep or at the bottom of a pitcher of water 35 cm deep.
pitcher
poor absorbers are also...
poor emitters
how many types of mechanical energy are there and what are they?
potential and kinetic energy.
Density is directly proportional to
pressure
small amount of force over a smaller area increases..
pressure
pressure equation
pressure = force/area of application
how does lift relate to houses
pressure above a roof is less than the pressure inside the house when wind is blowing. This produces a lift that may result in the roof being blown off.
change is pressure is directly proportinal to
pressure change
Pressure due to liquid equation
pressure dur to liquid = weight density x depth
if you fill a u-shaped tube with water and place pistons on each end
pressure exerted against the left piston will be transmitred thoughout the liquid and against the bottom of the right piston
Bernoullis principle states that the
pressure of a fluid flowing horizontally decreases as the speed increases.
the rate of cooling of an object is approximately
proportional to the temperature difference T between the object and its surroundings
according to newtons law of cooling, the rate of cooling of an object is approxiamely
proprtinal to the temeprature difference between the object and its surroundings
displaced
pushed aside
relative
regarded in relation to something else. Depends on point of view, or frame or frame refrence. Sometimes refered to as "with respect to,"
how is specifc het capacity like thermal inertia?
reistance for a substance to change in its temperature.
energy transmitted by radiation is called
radiant energy
the suns heat is transmitted by a process known as
radiation
how can heat be removed?
radiation to space, by evaporation of rain falling through dry air, or by contact with cold surface
list the radiant energy in order of wavelength
radio waves, microwaves, infarred rasiation, visible light, UV radiation, x rays, and gamma rays
what is rotational speed expressed in?
revolutions per minute (RPM)
example of revolution
riders along the platform outer edge revolve around its axis.
centripetal froce is at _____ _______ to the motion of an object moving in a circle
right angle
If there is no _______, there will be no centrifugual force.
rotation
what types of energy are in a substance
rotational kinetic energy kinetic enrgy due to internal movement of molecules potential energy due to the forces between molecules
which part of the earths surface has the greatest rotational speed about Earths axis? Which has the greatest linear speed relative to Earths axis?
rotational speed is the same everywhere, the linear speed is greater
the same inital velocity, same final velocity and same mass yields
same change in momentum, velocity and impulse
Air is more compressed at
sea level than at higher altitudes
air is more compressed at
sea level than at higher altitudes
high temperture objects emit _________ wavelengths
short
Suppose both gliders have the same mass. They move toward each other at the same speed and expirence an elastic collison. Describe the motion after the collison.
since the collison is eleastic, the gliders reverse directions after colliding and move away from each other at a speed equal to their inital speed
aneroid barometer (without liquid)
small portable insrumentd that uses a small metal box that is partially exhausted with air and has a flexible lif that bends in or out as atmospheric pressure changes. motion of thelid is indicated on a scale by a mechnical spring and lever system. used to determine elevation calibrated with a altimeter.
stream lines are
smooth paths, or trajectories of the bits of fluid.
what does snow do to the Earth?
snow slows the escape of heat from Earths surface.
how can you add heat?
solar radiation, by long-wavelength Earth radiation, by moisture condensation by contact with warm ground
an immersed object displaces
some of the fluid in which it is immersed
What was archimendes's pricniple?
that an immersed object is buoyed up by a force equal to the weight of the fluid it displaces
centripetal force is given to any force..
that is directed at a right angle to the path of a moving object and that tends to produce a circular motion
Newton's Law of Universal Gravitation
states that every object attracts every other object with a force that for any two objects is directly proportional to the mass of each object
What does the law of conservation of momentum state?
that the momentum is conserved when there is no net external force
What did Galileo state?
that this tendency of a moving body to keep moving is natural and that every material object resists change to its state of motion. we call this property if a body to resist change inertia.
watt
the SI unit of power, equal to one joule per second
pascals
the SI unit of pressure, equal to one newton per square meter
How can you make something warm?
striking something with a hammer put flame in a liquid compress air in a tire pump rapidly
What are molecules energized by?
sunlight and kept in continual motion
cold is not cold; but is simply
the absense of heat
th lower the effciency of a machine...
the greater is the amount of energy wasted as heat
how are tangential speed and rotational speed related?
tangential speed is directly proportional to the rotational speed and the radial distance from the axis of rotation
tangential speed and rasial distance and rotational speeed relation
tangential speed ~ radial distance x rotational speed
heat is energy and
tangible
as thermal motion of atoms increases
temperature increases
suppose a high-flying jet cruise with a constant velocity when the thrust from its engines is constant at 80 000 N. What is the acceleration of the jet? What is the force of air resistance acting on the jet?
the acceleration must be zero because the velocity is not changing - velocity is constant since acceleration is zero, net force is also zero
pressure
the amount of force per unit of area
what results in the average Earth temperature?
the amount of solar radiation that strikes Earth exactly balances the terrestrial radiation Earth emits into space
buoyancy
the apparent loss of weight of objects when submerged in a liquid
why doesnt the pressure of the atmosphere break windows?
the atmopshereic pressure doesnt normally break windows because it acts on both sides of a window. So no net force is exerted by the atmophere on the windows
Because of the random motion of particles,
the atom and molecules in matter have kinetic energy.
Wheneveer something becomes warm
the average kinetic energy increases
How does inflating a balloon and letting it go illustrate Newton's third law? Give Newton's third law and describe what happens to the balloon to illustrate this concept.
the balloon is forcing the air out by compressing. This is the action force.
why does a mercury barometer act the way it does?
the barometer balances when the weight of the liquid in the tube exerts the same pressure as the atmosphere outside. if the atmospheric pressure increase, the mercury column will go higher than 76. The mercurary is literally pushed up by the atmospheric pressure.
if you place freezing water in two jugs, one black, one black like, and place them in front of a fireplace what happens?
the black one warms up more quickly because its a good emitter of energy, thus is a good absorber
a 1-liter container filled with mercury has a mass of 13.6 kg and weighs 133 N. When it is submerged in water, what is the buoyant force on it?
the bouyant foce equals the weight of 1 L of water, which is about 10 N. Because the volume of displaced water is 1 L
the apparent weight of a submerged object is its weight in air minus
the buoyant force
describe a ladybug in a whirling can
the can presses against the lady bugs feet and provides a centripetal force that holds it in a circular bath. the lady bug in turn presses aginst the floor of the can. neglecting gravity the only force exerted on the ladybug is the force of the can on its feet. from the outside of the can we can see that there is no centrifugual force exerted on the ladybug.
energy
the capacity to do work
As the automobile in figure 19.20 is being lifted, how does the change in oil level in the reservoir compare with the distance the automobile moves?
the car moves up a greater distance than the oil level drops, since the area of the piston is smaller than the surface area of the oil in the reservoir.
Gravity-like centrifugual force and actual gravitational force
the centrifugual force appears as a force in its own right, as real as the pull of gravity. However, there is a fundemental difference between the gravity-like centrifugual force and actual gravitational force. gravitational force is the interaction between one mass and another. But in a roatting frame of refrence the centrifugual force has no agent such as massm there is no interaction counterpart. Centrifugual force is an effect of rotation. it is not a part of an interaction and therefore cannot be a true force. This is why centrifugal force is refered to as fictioys force.
in a rotating spaceship the acceleration expirenced is ...
the centripetal/ centrifugual accelertaion due to rotation. the magntitudde of this accelration is fdirectluy propartinal to the radial distance and the square of the rotational speed
what concept underlies all machines?
the conservation of energy
universal gravitational constant
the constant G in the equation for Newton's law of universal gravitation; measures the strength of gravity
the pressure of a liquid at rest depends only on
the density and depth.
the pressure exerted by liquid at any point is proprtinal to what
the density of the liquid times the depth of that point below the liquids surface
lift
the differrence between these pressures produces a net upward force
buoyant force is the difference between...
the downward and unward force placed on a submerged oject by the fluid, and the direction of buoyant force is upward
Projectiles: in the vertical direction is there a force?
the downward force of gravity, it accelerates downward
how does the greenhouse relate the Earth?
the earth is transparent to solar radiation. The surface of earth absorbs this energy reradiates part of this at longer wavelengths. The energy that Earth radiates is called terrestrial radiation. Atmospheric gasses absorb and re-emit much of this long-wavelength terrestrial radiation back to Earth. so the long wavelength radiation that cant escape earth's atmosphere warms Earth. the current concern is that the increased level of carbon dioxide and other atmospheric gases in the atmosphere may further increase the temperature and produce a new thermal balance unfavorable to the atmosphere.
specific heat capacity
the energy required to raise the temperature of one gram of a substance by one degree Celsius
if the flow speed is not to great,
the flow may become turbulent and follow a changing, curling path
in steady flow, one small bit of fluid follows along the same path as
the fluid in front of it
What force is acting on a book on a table?
the force of gravity and support force
the work done is equal to
the force required to move it upward times the vertical distance it is moved
the change in momentum depends on...
the force that acts and the length of time it acts
Friction
the force that acts between materials that touch as they move past each other
Describe buoyant force on a boulder
the forces are greater at the deeper portion of the boulder. the forces acting horizontally against the sides cancel each other, so the boulder is not pushed sideways. But the forces acting upward against the bottom are greater than those acting downward against the top because of the bottom of the boulder sis deeper. The difference in upward and downward forces is the buoyant force.
if there is an attractive force between all objects, why do we not feel ourselves gravitating toward massive buildings in our vicinity?
the forces is relaitively small because the masses are mass compared to the mass of the earth
a single pulley, type 2 lever
the fulcrum is at the left end of the "lever" where the supporting rope makes contact with the pulley. the load is suspended halfway between the fulcrum and the input end of the lever, which is on the right end of the "lever" each newton of input will support 2 newtons of load. mechanical advantage is 2 the load is now supported by two strands of rope. this means each strand supports half the load. The force the woman applied to support the load is therefore only half the weight od the load
Describe the type 1 lever
the fulcrum is located between the force and the load, or between the input and output. (seesaw) push doen on one end and you will lift a load at the other you can increase force at the expense of the distance.
Describe Types 3 lever
the fulcum is at one end and the load is at the other. The input force is applied between them. (your biceps muscles are connected to the bones in your forearm this way. the fulcrum is you elbow and the load is in your hand. increases distance at the expense of the force (when you move your muscles a short distance, your hand moves a much greater distance.) the inpiy and output forces are on the same side of the fulcrum and therefore have the same direction.
when work is done on a gas by adiabatically compressing it,
the gas gains internal energy and becomes warmer
If a heavy person and a light person open their parachutes together at the same altitude and each wears the same size parachute, who will reach the ground first?
the heavy person will reach the ground first. The light person reaches terminal speed sooner, while the heavy person continues to accelerate until a greater terminal speed is reached.
the higher the operating temperature,
the higher the efficency of that engine
Carnots equation gives
the ideal efficency, or Carnot efficency
Why is impulse greater when an object bounces?
the impulse required to bring the object to a stop and then throw it up again is much more then the impulse required to bring it to a stop
gravitation decreases according to
the inverse sqaure law. The force of gravity wekaens as the distance squared.
a chunk of iron has a temperature of 0 C. If a second, identical chunk of iron is twice as hot (has twice the absolute temperature), what is its temperature in degrees Celsius?
the iron twice as hot will be 273, because the 0 C chunck has an absoulte temperature of 273 K, which when doubled to 546 K. to convert to celcius simply subtract 273 from K.
the warmth you feel when you touch a hot surface is
the kinetic energy transfered by molecules in the surface to molecules in your fingers
the greater an ropes angle from the vertical ...
the larger tension force in them
the greater the speed of flow,
the less force of the water at right angles to the direction of slow
Describe the type 2 lever
the load is between the fulcrum and the input force to lift a load, you lift the end of the lever (placing a bar under a car frame and lifting on the free end to raise the automobile) force on the load is increased at the expense of distance Since the input and output forces are on the same side, the forces have the same direction
Mass
the measure of the amount of material in an object
how can you figure out the mechanical advantage?
the mechanial advantage for simple pulley systems is the same as the number of strands of rope that avtually support the load. in the first pulley system one strand supports the load so the mechnical advantage is 1, in the second it is supported by 2 so the mechanical advantage is 2
which bottle has more presssure at the bottom, a 1 liter bottle of mercury (hg) or 1 liter bottle of water?
the mercury because it is more dense
Describe gasses
the molecules are far apart, allowing them to move freely between collisions. When two molecules in a gas collide if one gains speed in the collision, the other loses speed, such that their total kinetic energy remains unchanged. A gas expands to fill all space available to it and takes the shape of its container. Only when the quantity is large, does gravitation determine the shape of the gas.
Without suns energy what would happen to molecules?
the molecules would just end up as matter on the grounf
since the moon is gravitionally attracted to Earth, why does it not simply crash into Earth?
the moon would crash inro earth if its tangential velocity were reduced to zero, buy because it isnt it falls around the Earth
What is the net force that acts on the cart in figure 6.13? On the horse? On the ground?
the net force on the cart is P-f; on the horse F-P; on the ground F-f
If a system undergoes changes wherein all the forces are internal
the net momentum of the system before and after the event is the same
The mass of an object depends on what?
the number and kind of atoms
what happens when you do work on one end of the lever?
the other end does work on the load. If we push down, the load is lifted up. if the heat from friction is small enough to neglect, the work input will be equal to the work output
trains ride on a pair of tracks. For straight-line motion, both tracks are the same length. But which track is longer for a curve, the one on the outside or the one on the inside of the curve?
the outside track is longe, just as a circle with a greater radius has a longer circumfrence.
Can you think of a case where a roller skate and a truck would have the same momentum?
the roller skate and truck can have the same momentum if the speed of the roller skate is much greater than the speed of the truck. It would have to be as many times greater as the truck's mass is greater than the roller skates mass. For example, a 1000 kg truck that has a speed of 0.01m/s has the same momentum as a 1-kg skate going 10 m/s. Both have a momentum of 10 kg m/s.
2. on a particular merry-go-round, the horses along the outer rail are located three times farther from the axis of rotation than te horses along the inner rail. If a boy sitting on a horse near the inner rali has a rotational speed of 4 RPM and a tangential speed of 2 m/s, what will be the rotational sppeed and tangential speed of his sister who is sitting on a horse along the outer rail?
the rotational speed of the siser is also 4 RPM. Her tangential speed is 6 m/s. Since the merry-go-round rigid, all the horses have the same rotational speed. But the horse at the outer rail is three times the distance from the center and thus has 3 times the tangential speed.
describe briefly a rotaing system
the rotational speed remains the same at all parts the linear and tangential speed caries. Tangential speed depedns on rotational speed and the distance from axis of rotation
If a car can accelerate at 2 m/s2, what acceleration can it attain if it is towing another car of equal mass?
the same force on twice the mass produces half the acceleration, or 1m/s^2
a block is held suspended beneath the water in three positions, A, B, C. In which position is the buoyant force on it greatest?
the same, because the amount of water displaced for all three us the same.
How does Bernoulli's Principle relate an airplane?
the shape and orintation of the wings ensures that air passes somethat faster over the top surface of aings rather than beaneath the lower surface. pressure above the wing is less than the pressure below
what happens to a automobile when it rounds a corner?
the sideways-acting friction between the tires and road provides a centripetal force that holds the car on a curved path. If the force of friction is not great enough, the car fails to make the curve and the tires sslide sideways. The car skids.
the greater the distance...
the smaller the force
instantaneous speed
the speed at any instant
terminal speed
the speed at which the acceleration of a falling object is zero becasue friction balances the weight
tangential speed
the speed of something moving along a circular path
If the children on the swings are equal in weight which is more likely to break, a vertical or slanted swing?
the stretching force, or tension is greater in the ropes hanging at an angle. The angeled ropes are most likely to break.
Science is...
the study of nature's rules
how does greenhouse effect relate to a car?
the suns hot temperature creates short wavelengths. These short wavelengths pass easily through both earths atmosphere and the car windows. so the suns energy gets in the car, where it is absorbed. the interior of the car warms up the car then radiates its own waves, but the waves are now longer. since the interiors temperature is much lower. the rereadiated long waves encounter opaque glass windows. so the energy remians in the car, which makes the caes interior even warmer. As hot as it gets, it wont be hot enough to eadiate wabes that pass back through the window
if you continually decrease the thermal motion of atoms in a substance
the temperature will drop
elapsed time
the time that has passed since the beginning of an event
internal energy
the total energy stored in the atoms and molecules within a substance
Describe how centripetal force related to a washing machine?
the tub roatets at a high speed during its spin cycle. the tubs inner wall exerts a centripetal force on the wet clothes, which are forced in a circular path. the tub exerts a great centripetal force on the clotehss but the holdes in the tub prevent it from exerting that force on the water. The water escapes because it tends to move by inertia in a straight line path unless acted on by a centripetal force or any other force.
the unit of force is a combination of what?
the unit of force, N the unit of distance, m
buoyant force
the upward force exerted by a fluid on a submerged object
what is net force?
the vector sum of all forces acting on an object and it affects the objects state of motion
resultant
the vector sum of two or more component vectors; the diagonal of the rectangle described by two vectors
a liquid in a container exerts force on...
the walls and bottom of the container
greenhouse effect
the warming effect whose cause is that short-wavelength radiant energy from the sun can enter the atmoosphere and be absorbed by Earth more easily than long-wavelength energy from Earth can leave
if we submerge 1-L water all the way, it will be buoyed up by a force equal to
the weight of a full liter of water
if a 1-L container is immersed half way into water, it will displace half a liter of water and be bouyed up by
the weight of half a liter of water
atmospheric pressure is caused by
the weight of the air
What does buoyant force depend on?
the weight of the displaced fluid
the amount of gravitational potential energy possessed by an elevated is equal to
the work done against gravity by lifting it
*in a simple case, where force is constant and the motion takes place in a straight line in the direction of the force, how can work be described?
the work done on the object by an applied force is the product of the force and the distance through which the object is moved
the kinetic energy of a moving object is equal to
the work required to bring it to its speed from rest, or the work the object can do while being brought to rest
If a good absorber were not a good emitter,
then black objects would remain warmer than light-colored objects and never come to thermal equilibrium
when a liquid is pressing against a surface,
there is a net force directed perpendicular to the surface
Is there a buoyant force acting on you? If there is, why are you not buoyed up by this force?
there is, and you are buoyed upward by it. You dont notice it because your weight is so much greater
From within a rotating frame of reference,
there seems to be an outwardly directed centrifugual force, which can stimulate gravity
But objects in thermal contact do come to
thermal equilibrium
specific heat capcity can be thought of as
thermal inertia
What are the charcateristics of a satellite?
they are fast moving projectiles that orbit the earth have a horizontal velocity that is so great that they continue to fall but never reach earths surface.
which is larger, a celcius degree or a Kelvin?
they are the same equal
At terminal speed what happens to the force of air resistance and forces of gravity?
they balance each other out.
no machine can create energy;
they can only transder energy from one place to another ot transform it from one form to another
Why do astronauts in a space shuttle float in a weightless conditon, whereas astronauts orbiting in some future rotating space station will expirence normal gravity?
they feel weightless because they lack a support force. They are not pressed against a supporting floor by gravity, nor do they expirence a centrifugual force due to spinning. Future space travelers need not be subject to weightelessness, because theyre space station will spin faast enough to supply a supporting force and stimulate gravity.
because atoms and molecules are constanltky in motion,
this means they have kinetic energy
Why do we insulate our homes?
to keep the heat in
for a steady flow of ideal fluid free of iinternal friction there are _____ kinds of energy. what are they
three kinetic --> due to motion work --> associated with pressure forces gravitational potential energy --> due to elevation
if you squeeze a balloon to one-third its volume, by how much will the pressure inside increase?
three times
what can "how long" mean?
time and distance
Energy is the capacity
to do work
at what point iin its path does does a projectile have minimum speed?
top, zero
average speed formula
total distance covered/time interval
average speed
total distance divided by total time
heat will flow from a warmer object to a coller object, but not necissarly from a object with more ______ _______ ___________ __________ to one that has less __________ __________ __________ _________.
total molecular kinetic energy ; total molecular kinetic energy
insulators cannot _______ ______ heat from getting theough, it can only ______ the rate at which heat penetrates
totally prevent; reduce
heat is the energy
transfer between substances due to differences in temperature
heat is the energy
transfer between to things due to a temperature difference
according to pascals principle, changes in pressure at any point in an enclosed fluid at rest are
transmitted undiminished to all points in the fluid and act in all directions
centrifugual force is not a
true force
How many categories does work fall into and what are they?
two --> work done against another force --> work done to change the speed of an object
Describe two balls falling one like a projectile, and one vertically?
two important things to notice --> is that the balls horizontal component of motions remains constant. The ball moves the same horizontal distance in the equal time intervals, since no horizontal component is acting on it. Gravity acts downward, so thats the only acceleration acting on it. --> is that both balls fall the same vertical distance in the same time
inversly proportional
two values changing in opopisite directions
pressure is a force per
unit area on which the force acts.
the calories and Calorie are
units of energy
When an object moves with a constant velocity while an applied force acts on it, an equal but opposite force. ..
usually friction, must also act to balance the force.
Liquids and gases are
usually good insulators.
velocity and distance traveled equation
v = at ; d=1/2at^2
Simplified instantaneous speed equation
v = gt ; v-velocity and speed, g= 10m/s, t- time
Is momentum a scalar or vector quantity?
vector
If we change either speed or direction, or both, we change...
velocity and acceleration
Which affects KE more, Mass or Velocity?
velocity becasue the equation is 1/2mv^2
A projectile is launched at an angle into the air. Neglecting air resistance, what is its vertical acceleration? Its horizontal acceleration?
vertical acceleration - 10 m/s^2 g horizontal acceleration - 0 no horizontal force
Which can support more weight, a horizontal clothline or vertical?
vertical, becasue there is much less tensioin
if an object is not hot enough, some of the radiant energy it emits is in the range of
visible lights
Mass is not the same as
volume
the volume of a submerged object is equal to the _____ of the liquid dispalced
volume
inverse square law
when a quantity varies as the inverse square of its distance from its source
Revolution
when an object turns about an external axis
Rotation
when an object turns around an internal axis, an axis locted within the body of the object; rotation = spin
thermal contact
when heat flows from one object or substance to another one it is in contact with
How does a thermometer work?
when it is contact with the substance, heat flows between them until they both have the same common temperature
what happens to objects that collide in the absense of external forces?
when objects collide in the absense of exteral forces, the momentum is conserved no matter whether the collision is elastic or inelastic.
Temperature is the measurment that tells how
warm or cold something is
the direction of spontaneous energy transfer is always from
warmer substance to a coller substance
The average kinetic energy of these particles causes an effect we can sesne that is called
warmth
Describe how a straw related to atmospheric pressure
when sucking on a straw, the liquid is not being sucked up, it is being pulled up by the pressure of the atmosphere. when you suck on the straw, you reduce the air pressire in he stae that is placed in the drink. Atmospheric pressure on the liquids surface pushes liquid up into the reduced pressire region.
when do forces cancel?
when the net forces are both internal; acting on the same object
Bernoulli's Principle
when the speed of a fluid increases, the pressure drops
Describe the crushing can expirement
water in is heated turns into gas and expands taken off heat turns back into water and shirnks the pressure goes up and down
which has a higher heat capacity - water or sand?
watrr has a higher heat capacity. Water is much slower to warm in the hot sun and slower to cool in the cold night. Water has more thermal inertia. Sajds low heat capcity is evident by how quickly it warms in the morning sun and how quickly it cools down
objects of everyday temperatures emit
waves that are mostly in the long end of the infared region, which is between radio and light waves
When momentum, or any quantity in physics, does not change
we say it is conserved.
Mass is not the same as
weight
the weight od a floating object is equal to the ______ of liquid displaced
weight
the total pressure of a liquid is
weight density x depth plus the pressure of the atmospheric
What is weight and what does it depend on?
weight on an object is the gravitational force acting on it Weight depends on the location of the obejct
the upward force required while moving at constant velocity is equal to the weight, mg, of the object, so the work done in lifting it rheoug a height h is the product of mgh.
what is the product of mgh?
in a steady flow where no energy is added or taken away,
whatever work is done by one part of the fluid on another part makes its apperance as kinetic and potential energy.
what is the relationship between work and energy?
work changes kinetic energy if no change in energy occurs, no work is done
Power equation
work done/time interval
the heavier an object, the more
work is done
Is time and force important in momentum change?
yes
does a 2-kilogram bunch of bananas have twice as much inertia as a 1-kilogram loaf of bread? Twice as much mass? Twice as much volume? Twice as much weight, when weighed in the same location
yes
is accelertaion in the same direction as net force?
yes
is air resistance considered friction?
yes
Is it important to define whats inside a system and outside?
yes because if we add heat energy, these system will be able to do work on external things.
Once the horse gets the cart up to the desired speed, must the horse continue to exert a force on the cart?
yes but only enough to counteract wheel friction and air resistance
newtons second law states that if no net force is exerted on a system, no acceleration occurs. Does it follow that no change in momentum occurs?
yes, because no accerlaerayion means that no change occurs in velocity or in momentum. No net force means there is no net impulse and thus no change in momentum
newtons third law states that the force a cannon exerts on a cannonball is equal and opposite to the force the cannonball exerts on the cannon. Does it follow that the impulse the cannon exerts on the cannonball is equal and opposite to the impulse the cannonball exerts on the cannon?
yes, because the cannon acts on the cannonball and the cannonball acts on the cannon during the same time interval. since time is equal and opposite, the inpulses are also equal and opposute. impulse is a vector quantity and can be canceled.
We know that Earth pulls on the moon. Does the moon also pull on Earth? If so, which pull is stronger?
yes, equal but opposite
can an object move at constant velocity even when an outside force is applied to it?
yes, if friction is present in this case, the friction force just balances the applied force the net force is zero, so there is no acceleration
how much work is done on a 100-N boulder that you carry horizontally across a 10-m room?
you do no work on the boulder moved horizontally, because you apply no force in its direction of motion. It has no more PE across the room than it had initally.
What happens as you move away from the center of a rotaing platform?
you move faster, the tangential speed increases while your rotational speed stays the same. twice as far from the center, the tangential speed is twice as much
To increase the acceleration of an object, you must
you must increase the net force acting on it
Work done against another force requires...
you to force soemthing to move against the influence an opposing force - usually friction
difference between speed and velocity?
your speed can be constant but you velocity isnt always.
work energy relationship equation
ΔE = W
Δmomentum =
Δmass or Δvelocity
