Psychics Chapter 1
A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200 N, the sack's acceleration in meters per second per second is 0. 4.9 .infinite. 9.8. none of these
0
An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration in meters per second per second is approximately 5. 24 0 8.
0
Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet? half the sum of their original momentums 0 twice the sum of their original momentums impossible to determine without additional information
0
Which of the following quantities represent mass? Check all that apply. 12.0 lbs 0.34 g 120 kg 1600 kN 0.34 m 411 cm 899 MN
0.34 120kg
An apple weighs 1 N. When held at rest above your head, the net force on the apple is 1 N. 0 N. 0.1 N. 9.8 N. none of these
0N
A 1-kg chunk of putty moving at 1 m/s collides with and sticks to a 5-kg bowling ball that is initially at rest on a frictionless surface. The speed of the putty thereafter is 1/5 m/s. 1/4 m/s. 1/6 m/s. impossible to solve with the information given.
1/6 m/s.
free fall how fast? The velocity acquired by an object starting from rest is velocity = acceleration x time So, under free fall, when acceleration is 10 m/s2, the speed is
10 m/s after 1 s. 20 m/s after 2 s. 30 m/s after 3 s. And so on.
So, under free fall, when acceleration is 10 m/s2, the speed is
10 m/s after 1 s. 20 m/s after 2 s. 30 m/s after 3 s. And so on.
An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about 5 m/s .15 m/s. 20 m/s. 10 m/s. not enough information given to estimate
10 m/s.
A car accelerates at 2 meters/s/s. Assuming the car starts from rest, how far will it travel in 10 s? 100 m 200 m 2 m 40 m 10 m
100 m
An object falls freely from rest on a planet where the acceleration due to gravity is 20 meters per second squared. After 5 seconds, the object will have a speed of 100 m/s. 5 m/s. 50 m/s. 20 m/s. 10 m/s
100 m/s.
An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about 5 m/s. 15 m/s .10 m/s. 20 m/s. not enough information given to estimate
10m/s
The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is more than 10 N. 10 N. less than 10 N.
10n
What is the net force when a pair of 5-N forces simultaneously act in the same direction on an object? 0N 5N 7.5N 10 N
10n a pair 5n moving in the same direction 5+5=10n
While you're in a bus that moves at 100 km/h, you walk from the back to the front at 10 km/h. What is your speed relative to the road outside? 90 km/h 100 km/h 110 km/h 10 km/h
110 km/h
Which of the following quantities would be acceptable representations of weight? Check all that apply. 12.0 lbs 0.34 g 120 kg 1600 kN 0.34 m 411 cm 899 MN
12.0 lbs 1600 kn 899 MN
It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft? about 120 m more than 200 m about 60 m about 180 m
180 m
Consider the video tutorial you just watched. Suppose that we duplicate this experimental setup in an elevator. What will the spring scale read if the elevator is moving upward at constant speed? View Available Hint(s)for Part A Less than 18 N but greater than 0 N More than 18 N 18 N 0N
18n
1 kg = on earth and moon
2.2 lb = 10 N at Earth's surface 1 kg = 1.7 N on the Moon
A karate chop delivers a blow of 3000 N to a board that breaks. The force that acts on the hand during this event is 6000 N. 3000 N .1500 N. zero.
3000n
A ball freely falling at 20 m/s will in the next second have a speed of _______. 20 m/s 30 m/s more than 30 m/s 10 m/s
30m/s
A car accelerates from rest for 5 seconds until it reaches a speed of 20 m/s. What is the car's acceleration in meters per second per second? 4 1 5 2 3
4
What is the net force acting on the box if 10 N act right and 5 N act left? 15 N to the left 15 N to the right 5 N to the left 5 N to the right
5 N to the right
Free Fall—How Far? The distance covered by an accelerating object starting from rest is distance=(1/2) x acceleration x time x time So, under free fall, when acceleration is 10 m/s2, the distance is
5 m after 1 s. 20 m after 2 s. 45 m after 3 s. And so on.
In a simple machine, how much work is done when an input of 10 N acts over a distance of 5 m? View Available Hint(s)for Part A 5 J 50 J 10 J 15 J
50 j
A person is attracted toward the center of Earth by a 500-N gravitational force. The Earth is attracted toward the person with a force of 1000 N. 250 N. 500 N. zero.
500 n
In its first second of free fall, a dropped softball will fall a vertical distance of _______. 15 m 10 m 20 m 5 m
5m
A 10-N falling object encounters 4 N of air resistance. The net force on the object is 10 N. 0 N. 4 N. 6 N. none of these
6n
A block is dragged without acceleration in a straight-line path across a level surface by a force of 6 N. What is the force of friction between the block and the surface? less than 6 N more than 6 N 6 N need more information to say
6n
Two 5-N vectors at an angle of 90° to each other have a resultant force of about _______. View Available Hint(s)for Part A 5 N 7 N 10 N 0 N
7n
What is the distance covered by a freely falling object starting from rest after 4 s? 4 m 16 m 40 m 80 m
80 m 1/2x10x4x4=80
A 2-kg mass is held 4 m above the ground. What is the approximate potential energy of the mass with respect to the ground? 32 J 8 J 80 J 6 J none of these
80j
A rock is thrown vertically into the air. At the top of its path, its acceleration in meters per second per second is greater than 9.8. zero. 9.8. between 0 and 9.8.
9.8
If you drop an object, it will accelerate downward at a rate of 9.8 meters per second per second. If you instead throw it downwards, its acceleration (in the absence of air resistance) will be less than 9.8 meters per second per second. greater than 9.8 meters per second per second. 9.8 meters per second per second.
9.8 meters per second per second. The acceleration due to gravity is always 9.8 m/s/s, regardless of the ball's velocity.
Consider the video demonstration that you just watched. Which of the following changes could potentially allow the ball on the straight inclined (yellow) track to win? Ignore air resistance. A. Increase the tilt of the yellow track. B. Make the downhill and uphill inclines on the red track less steep, while keeping the total distance traveled by the ball the same. C. Increase the mass of the ball on the yellow track. D. Decrease the mass of the ball on the red track.
A
Energy
A combination of energy and matter make up the universe. Energy Mover of substances Both a thing and a process Observed when it is being transferred or being transformed A conserved quantity -- trades off from place to place, time to time, as with momentum
static equilibrium
A condition where there are no net external forces acting upon a particle or rigid body and the body remains at rest or continues at a constant velocity example- hockey puck sitting at rest on ice.
Velocity
A description of the instantaneous speed of the object and what direction the object is moving Velocity is a vector quantity. It has magnitude/size: instantaneous speed direction: direction of object's motion
Gravity
A force of attraction between objects that is due to their masses. (Things tend to fall towards earth)
Non-Free Fall—Example
A skydiver jumps from plane. Weight is the only force until air resistance acts. Parachute maximizes air resistance. As falling speed increases, air resistance on diver builds up, net force is reduced, and acceleration becomes less. When air resistance equals the diver's weight, net force is zero and acceleration terminates. Diver reaches terminal velocity, then continues the fall at constant speed.
As the skydiver falls faster and faster through the air, air resistance A. increases. B. decreases. C. remains the same. D. Not enough information.
A. increases.
When Sanjay pushes a refrigerator across a kitchen floor at an increasing speed, the amount of friction between the refrigerator and the floor is A. less than Sanjay's push. B. equal to Sanjay's push. C. equal and opposite to Sanjay's push. D. more than Sanjay's push.
A. less than Sanjay's push. Explanation: The increasing speed indicates a net force greater than zero. The refrigerator is not in equilibrium.
When a 20-N falling object encounters 5 N of air resistance, its acceleration of fall is A. less than g. B. more than g. C. g. D. terminated.
A. less than g. Comment: Acceleration of a non-free fall is always less than g. Acceleration will actually be (20 N - 5 N)/2 kg = 7.5 m/s2.
The force of friction can occur A. with sliding objects. B. in water. C. in air. D. All of the above.
All of the above. Comment: Friction can also occur for objects at rest. If you push horizontally on your book and it doesn't move, then friction between the book and the table is equal and opposite to your push.
Newton's First Law of Motion: relation to galelio
An object at rest remains at rest (or, if in motion, remains in constant, straight-line motion) unless acted upon by a net force. Like coasting, without gravity or friction. = Galileo's idea of inertia.
A 5-kg iron ball and a 10-kg iron ball are dropped from rest. When the free-falling 5-kg ball reaches a speed of 10 m/s, the speed of the free-falling 10-kg ball is A. less than 10 m/s. B. 10 m/s. C. more than 10 m/s. D. undetermined.
B. 10 m/s.
A soccer player kicks a ball with 1500 N of force. The ball exerts a reaction force against the player's foot of A. somewhat less than 1500 N. b. 1500 N. c. somewhat more than 1500 N. d. None of the above.
B. 1500n
Consider a heavy and light person jumping together with same-size parachutes from the same altitude. Who will reach the ground first? A.The light person. B. The heavy person. C. Both will reach at the same time. D. Not enough information.
B. The heavy person Explanation: They both have the same drag force (for the same speed). The heavier person has a greater downward force than the lighter person. The heavy person will drop farther and speed up for a longer time before getting to where the drag force equals to his downward force, so has a higher terminal velocity.
Consider a high-speed bus colliding head-on with an innocent bug. The force of impact splatters the unfortunate bug over the windshield.Which is greater, the force on the bug or the force on the bus? A. Bug b. Bus c. Both are the same. d. Cannot say
Both are the same. Although the forces are equal in magnitude, the effects are very different. Do you know why? F/m for bug is much bigger than F/m for bus
When the air is removed by a vacuum pump and the coin and feather activity is repeated, A. the feather hits the bottom first, before the coin hits. B. the coin hits the bottom first, before the feather hits. C. both the coin and feather drop together side-by-side. D. Not enough information.
C. both the coin and feather drop together side-by-side. No air, no air resistance. All objects fall at the same rate in the absence of air resistance. This was verified by astronauts on the airless Moon.
Consider a cart pushed along a track with a certain force. If the force remains the same while the mass of the cart decreases to half, the acceleration of the cart A. remains relatively the same. B. halves. C. doubles. D. changes unpredictably. Hint: F = (m/2) (2a)
C. doubles. Explanation: Acceleration = net force / mass Because, mass is in the denominator, acceleration increases as mass decreases. So, if mass is halved, acceleration doubles.
When Sanjay pushes a refrigerator across a kitchen floor at a constant speed, the force of friction between the refrigerator and the floor is A. less than Sanjay's push. B. equal to Sanjay's push. C. equal and opposite to Sanjay's push. D. more than Sanjay's push.
C. equal and opposite to Sanjay's push.We are in dynamic equilibrium!
Which best describes what occurs when a body accelerates? Change in velocity per unit time Change Change in velocity Change in direction
Change in velocity per unit time
The size of the earth was first measured in ________ (place)
Egypt
Free Fall
Falling under the influence of gravity but with no air resistance. Freely falling objects on Earth accelerate at the rate of 10 m/s/s, i.e., 10 m/s2 (more precisely, 9.8 m/s2 or 32 ft/s/s).
Free Fall vs. Non-Free Fall Coin and feather fall with air present
Feather reaches terminal velocity very quickly and falls slowly at constant speed, reaching the bottom after the coin does. Coin falls very quickly and air resistance doesn't build up to its weight over short-falling distances, which is why the coin hits the bottom much sooner than the falling feather.
collisons
For all collisions in the absence of external forces net momentum before collision equals net momentum after collision. in equation form: (net mv)before = (net mv)after
Newton's second law equation example
Force = mass x acceleration If net force acting on object is doubled ⇒ object's acceleration will be doubled. If mass of object is doubled ⇒ object's acceleration will be halved.
Newton's Second Law
Force and mass determine the acceleration: a big force (push) causes a big acceleration, but a big mass will respond less than a small mass. Some common forces we will discuss are friction and weight.
In the apple-pulling-the-orange sequence in this chapter, what is the force that accelerates the system across the floor? View Available Hint(s)for Part A The backward pull by the orange The resistance to motion by the orange Friction between the apple and the floor Internal forces
Friction between the apple and the floor
Galileo's Concept of Inertia
Galileo demolished Aristotle's assertions in the 1500s. Galileo's discovery: Objects of different weight (paper-ball, lead ball) fall to the ground at the same time in the absence of air resistance. A moving object needs no force to keep it moving (in the absence of friction).
Non- free fall: air resistance force and gravity force both act. But air resistance depends on speed
If speed is very small, resistance is very small and acceleration is approximately g (negligible R). As speed increases, R resistance increases, balancing out more of gravity force -- acceleration gets smaller. Eventually, speed gets so big that resistance completely balances gravity force = no net force = no acceleration = terminal velocity.
Law of conservation of momentum:
In the absence of an external force, the momentum of a system remains unchanged. ie, the total momentum before = total momentum after.
A block of mass 2kg2kg is acted upon by two forces: 3N3N (directed to the left) and 4N4N (directed to the right). What can you say about the block's motion? View Available Hint(s)for Part C It must be moving to the left.It must be moving to the right.It must be at rest.It could be moving to the left, moving to the right, or be instantaneously at rest.
It could be moving to the left, moving to the right, or be instantaneously at rest.
When you step off a curb, Earth pulls you downward and you pull the Earth upward. Why do you not sense Earth moving upward toward you? A. Earth is fixed, so it cannot move. b. Earth can move, but other objects on it prevent it from moving.* c. It moves, but a very small amount that you cannot see. d. None of the above.
It moves, but a very small amount that you cannot see. Explanation: You exert a force on Earth that is equal to the force it exerts on you. But you move more than the Earth does, because its mass is so great compared to your mass that it moves very little and you do not notice it.
impulse
Product of force and time (force × time) Equivalent to the change in momentum (analogous to man-hours) In equation form: Impulse = Ft = momentum change Force x time = difference in mass x velocity Force x time = massxvelocity - massxvelocity Δ is symbol for "difference in" so Ft = Δ mv Example: A (brief) force applied over a short time interval produces a smaller change in momentum than the same force applied over a longer time interval. or If you push with the same force for twice the time, you impart twice the impulse and produce twice the change in momentum.
How does the force on the rifle compare with the force on the bullet, and why? The force on the rifle is less than the force on the bullet because the mass of the rifle is greater The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and the forces are in the opposite direction, because for every action there is an equal and opposite reaction. The force on the rifle is greater than the force on the bullet because the mass of the rifle is greater. The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and both forces are in the same direction, because for every action there is an equal reaction.
The magnitude of the force of the rifle is equal to the magnitude of force on the bullet and the forces are in the opposite direction, because for every action there is an equal and opposite reaction.
A Volkswagen bug and a Volvo truck have a head-on collision. Which statement is true? View Available Hint(s)for Part A Both forces are identical. The magnitudes of both forces are the same. The greater force acts on the Volkswagen bug. The greater force acts on the Volvo truck.
The magnitudes of both forces are the same.
Mass
The quantity of matter in an object. It is also the measure of the inertia or sluggishness that an object exhibits in response to any effort made to start it, stop it, or change its state of motion in any way. A measure of the inertia of a material object Independent of gravity Greater inertia ⇒ greater mass Unit of measurement is the kilogram (kg)
Acceleration
The rate at which velocity changes Involves a change in speed, or change in direction, or both. Example: Car making a turn
Resultant
The sum of two or more vectors For vectors in the same direction, add arithmetically. For vectors in opposite directions, subtract arithmetically. Two vectors that don't act in the same or opposite direction: use parallelogram rule. Two vectors at right angles to each other use Pythagorean Theorem: R2 = V2 + H2. V = vertical H = horizontal
Free Fall vs. Non-Free Fall Coin and feather fall in vacuum
There is no air, because it is vacuum. So, no air resistance. Coin and feather fall together.
Re-expression of Newton's third law:
To every action there is always an opposed equal reaction. Example: Tires of car push back against the road while the road pushes the tires forward.
the parallelogram rule
To find the resultant of nonparallel vectors we can use the parallelogram rule. consider two vectors at right angles to each other as shown below the constructed parallelogram in this special case is a rectangle the diagonal is the resultant r.
Mass versus weight on the Moon and Earth:
Weight of an object on the Moon is less than on Earth. Mass of an object is the same in both locations.
Non-Free Fall
When an object falls downward through the air it experiences force of gravity pulling it downward. air drag force acting upward. Both gravity and air drag act at the same time Net force Σ is the vector sum, causing acceleration if not in equilibrium occurs when air resistance is non-negligible. net force is smaller than free fall acceleration of fall is less than g air resistance depends on two things: speed and frontal surface area (shape, such as parachute).
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. FA on B = - FB on A Ex. Hammer hits nail (speeds up nail). Nail hits hammer (slows down hammer)
To get the same lift, compared with a lightweight glider, a heavier glider would have to push air A. downward with greater force. downward with the same force. downward with less force. None of the above.
a downward with greater force Explanation: The force on the air deflected downward must equal the weight of the glider.
Momentum
a property of moving things means inertia in motion more specifically, mass of an object multiplied by its velocity in equation form: Momentum = mass × velocity Example: A big moving boulder has more momentum than a small stone moving at the same speed. A fast boulder has more momentum than a slow boulder of the same mass. A boulder at rest has no momentum.
When a dish falls, will the change in momentum be less if it lands on a carpet than if it lands on a hard floor? a. No, both are the same. b. Yes, less if it lands on the carpet. c. No, less if it lands on a hard floor. d. No, more if it lands on a hard floor.
a. no both are the same Explanation: The momentum becomes zero in both cases, so both change by the same amount. Although the momentum change and impulse are the same, the force is less when the time of momentum change is extended. Be careful to distinguish among force, impulse, and momentum.
Galileo discovered that when air resistance can be neglected, all objects fall with the same _______. energy of motion acceleration distance speed
acceleration
If an object of constant mass experiences a constant net force, it will have a constant speed. acceleration. velocity. position. more than one of the above
acceleration
When we're talking about how quickly "how fast" changes, we're talking about _______. increases in falling distance acceleration the difference between speed and velocity free-fall physics
acceleration
Scalar measurements are shown on odometers, which tell you the _____ wear and tear on your tires regardless of direction: backing up does not subtract mileage from your tires (4 + 3 = 7).
accumulated
A car traveling along the highway needs a certain amount of force exerted on it to stop it in a certain distance. More stopping force is required when the car has more momentum. more mass. less stopping distance. all of these none of these
all of these
Which has zero acceleration? An object in mechanical equilibrium. moving at constant velocity. at rest. all of these none of these
all of these
Science, art, and religion do not contradict one another because if you choose the right one, you can forget the other two .if you choose religion and art, you can forget about science. if you choose science, you can forget about religion and art. all three have different domains.
all three have different domains.
A fact in science is _______.
an agreement between trained investigators
force
any push or pull
The center of gravity of a basketball is located _______. View Available Hint(s)for Part A at a point opposite to its center of mass in the material making up its mass at its geometrical center at the point of application when balanced
at its geometrical center
Newton had interpreted gravity as an
attraction between bodies with mass things that have mass attract each other like moons and planets and thats what hold them in the patterns we see
If a 50-N person is to fall at terminal speed, the air resistance needed is A. less than 50 N. B. 50 N. C. more than 50 N. D. None of the above.
b. 50 N Explanation: Then, ΣF = 0 and acceleration = 0.
As the skydiver continues to fall faster and faster through the air, her acceleration A. increases. B. decreases. C. remains the same. D. Not enough information.
b. decreases. Comment If this question were asked first in the sequence of skydiver questions, many would answer it incorrectly. Would this have been you
Freight car A is moving toward identical freight car B that is at rest. When they collide, both freight cars couple together. Compared with the initial speed of freight car A, the speed of the coupled freight cars is A. the same. b. half. c. twice. d. None of the above.
b. half Explanation: After the collision, the mass of the moving freight cars has doubled. Can you see that their speed is half the initial velocity of freight car A?
A fast-moving car hitting a haystack or hitting a cement wall produces vastly different results.1. Do both experience the same change in momentum?2. Do both experience the same impulse?3. Do both experience the same force? A. Yes, yes, yes b. Yes, yes, no c. No, no, no d. No, no, yes
b. yes yes no Explanation: Although stopping the momentum is the same whether done slowly or quickly, the force is vastly different. Be sure to distinguish among momentum, impulse, and force.
You are riding in a van at a steady speed and toss a coin up. Where will the coin land? behind you ahead of you back in your hand There is not enough information
back in your hand
An Interaction is
between one thing and another. requires a pair of forces acting on two objects. Example: interaction of hand and wall pushing on each other Force pair—you push on wall; wall pushes on you.
A bowling ball is in equilibrium when it is at rest. moves steadily in a straight-line path. Both of the above. None of the above.
both of the above
An automobile is accelerating when it is slowing down to a stop. rounding a curve at a steady speed. Both of the above. Neither of the above.
both of the above change in speed and change in direction
What task requires the most work; lifting a 50-kg sack 2 meters or lifting a 25-kg sack 4 meters? the 50-kg sack the 25-kg sack Both require the same amount of work. impossible to determine without knowing the contents of the sack
both require the same amount of work
When traveling twice as fast your kinetic energy is increased _______. View Available Hint(s)for Part A by three not at all by two by four
by four
When you step off a curb, Earth pulls you downward. The reaction to this force is A. a slight air resistance. b.nonexistent in this case. c.you pulling Earth upward. d. None of the above.
c. you pulling Earth upward. (mass) (acceleration) = - (mass) (acceleration) A and B are you and the Earth. Earth has a huge mass compared to you
Two forces, of magnitude 4N4N and 10N10N, are applied to an object. The relative direction of the forces is unknown. The net force acting on the object __________. Check all that apply. cannot have a magnitude equal to 5N cannot have a magnitude equal to 10N cannot have the same direction as the force with magnitude 10N must have a magnitude greater than 10N
cannot have a magnitude equal to 5n
If an object moves with constant acceleration, its velocity must change by the same amount each second. always decrease. be constant also. change by varying amounts depending on its speed.
change by the same amount each second
When lift is greater, the helicopter A. climbs down. b.climbs up. c.hovers in midair. d.None of the above.
climbs up
Your car is coasting on level ground at 60 km/h and you apply the brakes until the car slows to 40 km/h. If you suddenly release the brakes now, the car tends to decrease in speed if no other forces act. momentarily regain its higher initial speed. continue moving at 40 km/h.
continue moving at 40 km/h.
When bullets are fired from an airplane in the forward direction, the momentum of the airplane will be unchanged. decreased. increased.
decreased
The Force of Friction example
depends on the kinds of material and how much they are pressed together. is due to tiny surface bumps and to "stickiness" of the atoms on a material's surface. Example: Friction between a crate on a smooth wooden floor is less than that on a rough floor.
Energy cannot be _______. View Available Hint(s)for Part A transferred destroyed transformed transferred, transformed, or destroyed
destroyed
The difference between speed and velocity involves _______. acceleration the magnitude of each path length direction
direction
it is often easier to _____ a never statement than to _____ an always statement
disprove, aprove
When the force that produces an impulse acts for twice as much time, the impulse is A. not changed. b. doubled. c. quadrupled. d. halved.
doubled
When the rotational speed of a rotating system doubles, its angular momentum _______. View Available Hint(s)for Part A remains unchanged reduces to zero doubles quadruples
doubles
When the speed of an object is doubled, its momentum A. remains unchanged in accord with the conservation of momentum. b. doubles. d. quadruples. d. decreases.
doubles
When a cannonball is fired from a cannon, the momentum of the recoiling cannon is momentarily _______. View Available Hint(s)for Part A less than the momentum of the fired cannonball the same as that of the fired cannonball equal and opposite to the momentum of the fired cannonball greater than the momentum of the fired cannonball
equal and opposite to the momentum of the fired cannonball
You are pushing a crate at a steady speed in a straight line. If the friction force is 75 N, how much force must you apply? more than 75 N less than 75 N equal to 75 N not enough information
equal to 75 n
Whereas Aristotle relied on logic in explaining nature, Galileo relied on patterns. logic also. mathematics. experiment.
experiment
What is required to change the angular momentum of a system? View Available Hint(s)for Part A External force Torque External torque Force
external torque
A boxer rides with the punch so as to reduce _______. View Available Hint(s)for Part A momentum speed force impulse
force
The newton is a unit of mass. density .inertia .force.
force
Free fall acceleration depends on
force (weight) and inertia.
The torque exerted by a crowbar on an object increases with increased _______. View Available Hint(s)for Part A rotational inertia energy of application force force and leverage distance
force and leverage distance
weight
force on an object due to gravity. Weight = force of earth pulling an object Weight = mass x 10 (or 9.8 to be precise) The force on an object due to gravity Proportional to mass Scientific unit of force is the newton (N) Unit (US Customary) is the pound (lb)
A player catches a ball. Consider the action force to be the impact of the ball against the player's glove. The reaction to this force is the friction of the ground against the player's shoes. muscular effort in the player's arms. player's grip on the glove. force the glove exerts on the ball. none of these
force the glove exerts on the ball.
The work that is done when twice the load is lifted twice the distance is _______. View Available Hint(s)for Part A the same four times as much three times as much twice as much
four times as much
When you lift twice the load twice as high, in half the time, the increase in potential energy is _______. View Available Hint(s)for Part A three times as much four times as much double the same
four times as much
A coconut and a feather fall from a tree through the air to the ground below. The amount of air-resistance force is greater on the feather. the same on each. greater on the coconut.
greater on the coconut.
The tangential speed on the outer edge of a rotating carousel is _______. View Available Hint(s)for Part A the same as toward the center less than toward the center greater than toward the center four times as great for twice the distance
greater than toward the center
If the mass of an object is halved, the weight of the object is A. halved. B. twice. C. depends on location. D. None of the above.
halved.
Vector quantity
has magnitude and direction. is represented by an arrow. Example: velocity, force, acceleration
Scalar quantity
has magnitude. Example: mass, volume, speed
Cassy can get more force on the bricks she breaks with a blow of her bare hand when _______. View Available Hint(s)for Part A she toughens her hand beforehand she does so with great determination she exerts follow through her hand is made to bounce from the bricks
her hand is made to bounce from the bricks
When lift equals the weight of a helicopter, the helicopter A. accelerates down. b. accelerates up. c. hovers in midair. d. None of the above.
hovers in midair.
Follow through is important in golf because it results in a greater force on the ball impulse on the ball force and greater impulse on the ball swinging motion
impulse on the ball
Rotational inertia about the midpoint of an object becomes greater with _______. View Available Hint(s)for Part A decreased mass and decreased distance to mass concentration increased mass and increased distance to mass concentration decreased mass increased mass
increased mass and increased distance to mass concentration
As a skydiver gains speed in falling through the air, air resistance _______. View Available Hint(s)for Part A decreases increases cancels weight becomes negligible when terminal speed is reached
increases
If one object has twice as much mass as another object, it also has twice as much inertia. acceleration due to gravity. velocity. volume. all of these
inertia.
A speedometer normally measures _ distance traveled instantaneous speed average speed velocity
instantaneous speed
Mass and weight in everyday conversation are
interchangeable
For an action force, there must be a reaction force that is slightly smaller in magnitude than the action force. is slightly larger in amplitude than the action force. always acts in the same direction. is exactly equal in magnitude.
is exactly equal in magnitude.
Air resistance on a parachutist at terminal speed _______. View Available Hint(s)for Part A is the same for both a heavy and light person with the same size parachutes no longer depends on speed is greater for a heavier person is less for a heavy person
is greater for a heavier person
A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the water depends on how high they started. is greater for the fired bullet. is greater for the dropped bullet. is the same for each bullet. none of these
is the same for each bullet.
What is the acceleration of the ball when it is moving up, when it is at the maximum height, and when it is moving down? (Note: The acceleration graph is shown in red.) It is always zero. The acceleration is negative when the ball is moving up, zero at the top, and positive when the ball is moving down. It is always positive. It is always negative.The acceleration is positive when the ball is moving up, zero at the top, and negative when the ball is moving down. Submit
it is always negative. In fact, the acceleration due to gravity is always 10 m/s2 downward. In other words, it is -10 m/s2.
What is the value of the velocity of the ball when it reaches its maximum height? It is either positive or negative, depending on the initial velocity. It is always positive. It is always negative. It is always zero.
it is always zero
A slowly moving ship can have a greater momentum than a fast-moving racing car when _______. its mass is greater than the mass of the car its speed is greater than the speed of the car it drifts toward a distant port its mass times velocity is greater than that of the car
its mass times velocity is greater than that of the car
When you are in the way of a fast-moving object and can't get out of its way, you will suffer a smaller force of impact if you decrease its momentum over a short time. long time. same way either way
long time
A kilogram is a measure of an object's size. weight. mass. force.
mass
An object is lifted from the surface of a spherical planet to an altitude equal to the radius of the planet. As a result, which of the following changes in the properties of the object take place? mass increases; weight decreases mass decreases; weight decreases mass increases; weight increases mass increases; weight remains the same mass remains the same; weight decreases mass remains the same; weight increases mass remains the same; weight remains the same
mass remains the same weight decreases
When a cannon is fired, the accelerations of the cannon and cannonball are different because the A. forces don't occur at the same time. b. forces, although theoretically the same, in practice are not. c. masses are different. d. ratios of force to mass are the same.
masses are different.
A free-falling object has a speed of 30 m/s at one instant. Exactly 1 s later its speed will be the same. 35 m/s. more than 35 m/s. 60 m/s.
more than 35m/s One second later its speed will be 40 m/s, which is more than 35 m/s.
A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be __________. View Available Hint(s)for Part D continuously changing direction moving at constant velocity moving with a constant nonzero acceleration moving with continuously increasing acceleration
moving with a constant non zero accretion
A ball rolling down an incline has its minimum speed half way down the incline. near the top of the incline. at the end the incline. impossible to predict without knowing the ball's mass impossible to predict without knowing the size of the ball
near the top of the inclince
Acceleration is equal to g when air resistance is
negligible
Acceleration depends on and is directly proportional to the
net force
An object's weight may properly be expressed in units of cubic centimeters. kilograms. newtons. meters.
newtons.
Compared to a 1-kg block of solid iron, a 2-kg block of solid iron has the same mass. volume. weight. all of these none of these
none of these
Terminal speed
occurs when acceleration terminates (when air resistance equals weight and net force is zero)
Elastic collision (bounce off)
occurs when colliding objects rebound without lasting deformation or any generation of heat. Initial momentum is transferred to other object
Inelastic collision (stick together)
occurs when colliding objects result in deformation and/or the generation of heat. objects stick together after collision Initial momentum becomes shared
Slightly tilted wings of airplanes deflect A. oncoming air downward to produce lift. B. oncoming air upward to produce lift. C. Both of these. D. Neither of these.
oncoming air downward to produce lift Explanation: When a wing diverts air downward, it exerts a downward force on the air. The air simultaneously exerts an upward force on the wing. The vertical component of this upward force is lift. (The horizontal component is drag.)
Newton's Third Law of Motion Action and reaction forces
one force is called the action force; the other force is called the reaction force (doesn't matter which is called which). are co-pairs of a single interaction. neither force exists without the other. are equal in strength and opposite in direction. always act on different objects.
Vector distance is useful for finding how far something has traveled as-the-crow flies: if you drive four miles east, then three miles west, you end up
one mile east of where you started (+4 + -3 = +1).
The direction of the force of friction on a sliding crate is _______. opposite to the direction of sliding in the same direction as the force that produces sliding nondirectional usually at right angles to the force that produces sliding
opposite to the direction of sliding
the upward support force is ____ and the downward is ______. therefore they ___ mathematically to equal ____
positive, negative, add, zero
A job is done slowly, while an identical job is done quickly. Both jobs require the same amount of work, but different amounts of power. effort. energy. none of these
power
The team that will win in a tug-of-war is the team that _______. View Available Hint(s)for Part A pushes harder on the floor while holding the rope has the greater self confidence. yanks the rope pulls with the greater force
pushes harder on the floor while holding the rope
A bird flies by A. flapping its wings. B. pushing air down so that the air pushes it upward. C. hovering in midair. D. inhaling and exhaling air.
pushing air down so that the air pushes it upward.
When hitting a tennis ball with your racquet, the force on the ball has the same magnitude as the force on the _______. View Available Hint(s)for Part A racquet racquet, and in the same direction hand that holds the racquet player
racquet
When a big fish swims into an oncoming smaller fish and swallows it, the momentum of the two-fish system _______. View Available Hint(s)for Part A converts to spurious motion remains the same increases decreases
remains the same
Terminal velocity
same as terminal speed, with direction implied or specified.
Since each rolling wheel of a railroad train is tapered, the narrow part of the wheel has a tangential speed that is greater than that of the wide part. the same as that of the wide part. smaller than that of the wide part.
smaller than that of the wide part
A scientific hypothesis must be
testable it is more important that there be a way of proving it wrong than that there be a way of proving it correct if there is no test for its possible wrongness than it is not scientific.
hypothesis must be able to be
tested
Which has greater kinetic energy, a car traveling at 30 km/hr or a car of half the mass traveling at 60 km/hr? the 30 km/hr car the 60 km/hr car Both have the same kinetic energy. More information is needed about the distance traveled.
the 60 km/hr car
In the video, Dr. Hewitt drops a book and a flat piece of paper together from the same height. Which object that hits the ground first? The paper hits the ground first.The book hits the ground first.The book and paper hit the ground at the same time.
the book hits the ground first because of air resistance on the paper
The Greek mathematician Eratosthenes made measurements to show the size of Earth the Moon the Sun all of the given answers
the earth
Two identical freight cars roll without friction (one at 1 m/s, the other at 2 m/s) toward each other on a level track. They collide, couple together, and roll away in the direction that the faster car was initially going. the slower car was initially going. Neither of these. They stop.
the faster car was initially going
An object at rest cannot remain at rest unless which of the following holds? View Available Hint(s)for Part A The net force acting on it is zero.The net force acting on it is constant and nonzero.There are no forces at all acting on it.There is only one force acting on it.
the net force acting on it is zero.
If a block is moving to the left at a constant velocity, what can one conclude? View Available Hint(s)for Part B There is exactly one force applied to the block.The net force applied to the block is directed to the left.The net force applied to the block is zero.There must be no forces at all applied to the block.
the net force applied to the block is zero
The unit of mass is the kilogram, and the unit of weight is _______. View Available Hint(s)for Part A metric mass the kilogram also the newton m/s2
the newton
The attraction of a person's body toward Earth is called weight. The reaction to this force is the person's body pulling on the Earth. the Earth's surface pushing against the person's body. the person's body pushing against Earth's surface. none of these
the person's body pulling on the Earth.
The quantity that is called impulse can be measured by _______. the addition of force and time the product of force and time the difference between force and time how long the force acts compared to the amount of time
the product of force and time
A 1-kg stone and a 10-kg stone have the same acceleration in free fall because _______. View Available Hint(s)for Part A the ratio of weight to mass is the same for each the force of gravity is the same on each air resistance has no effect they both fall equally
the ratio of weight to mass is the same for each
A 5-kg iron ball and a 10-kg iron ball are dropped from rest. For negligible air resistance, the acceleration of the heavier ball will be ______ compared to the lighter ball. A. less. B. the same. C. more. D. undetermined.
the same
When one does twice the work in twice the time, the power expended is _______. View Available Hint(s)for Part A three times as much four times as much the same twice as much
the same
Each second, a ball rolling down an inclined plane picks up _______. the same amount of speed acceleration, not speed decreasing amounts of speed increasing amounts of speed
the same amount of speed
A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The force of impact is the same for both. greater on the bug. greater on the car.
the same for both
Fossil fuels, hydroelectric power, and wind power ultimately get their energy from _______. View Available Hint(s)for Part A the Sun potential energy Earth's nuclear energy greenhouse gases
the sun
What did Copernicus say about the motion of the Sun? The Sun rises and falls each 24 hours .The Sun is stationary and the Earth circles it. The Sun circles the Earth each 365 days. The Sun circles the Earth each 24 hours.
the sun is stationary and the earth circles it.
A boxer cannot exert much force on a piece of tissue paper suspended in air because _______. View Available Hint(s)for Part A there is little follow-through with the punch the tissue paper has too little mass to exert much force on the boxer's fist the tissue lacks enough strength the time of the interaction is too brief
the tissue paper has too little mass to exert much force on the boxer's fist
support force
the upward force that balances the weight of an object on a surface
When you push against a wall, what pushes back? View Available Hint(s)for Part A Nothing The wall Your hand Your fingers
the wall
The synthesis of a large collection of information that contains well-tested and verified hypotheses about certain aspects of the world is known as a scientific hypothesis. law or principle. fact. theory. none of these
theory
When Dr. Hewitt drops a book and a crumpled piece of paper together from the same height, which one hits the ground first? View Available Hint(s)for Part C The book hits the ground first.The crumpled paper hits the ground first.They both hit the ground at the same time.
they both hit at the same time because not as much air resistance is acting on the paper.
To catch a ball, a baseball player extends the hand forward before impact with the ball and then lets it ride backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because the time of impact is increased. force of impact is reduced. relative velocity is less. time of impact is decreased. none of these
time of impact is increased
When a cue ball strikes an 8 ball head-on in a game of pool, the cue ball _______. View Available Hint(s)for Part A moves off at an angle transfers its momentum to the 8 ball slows in its speed retains its initial momentum
transfers its momentum to the 8 ball
Recycled energy is mainly _______. View Available Hint(s)for Part A energy that has been destroyed thermal energy kinetic or potential energy use of energy otherwise wasted
use of energy otherwise wasted
force is a
vector
When a falling firecracker explodes, the momenta of its pieces _______. View Available Hint(s)for Part A illustrate a case in which momentum is not conserved disintegrate vectorally add to equal the initial momentum of the firecracker are conserved only if the fragments eject in one direction
vectorally add to equal the initial momentum of the firecracker
Whenever a net force acts on an object, there is a change in the object's _______. View Available Hint(s)for Part A shape direction speed velocity
velocity
Which of the following depends on gravity? View Available Hint(s)for Part A Force Mass Acceleration Weight
weight
The gravitational field on the surface of the earth is stronger than that on the surface of the moon. If a rock is transported from the moon to the earth, which properties of the rock change? mass only weight only both mass and weight neither mass nor weight
weight only
A crate sits at rest on a factory floor. Friction between the crate and floor occurs _______. only if the crate is sliding only if the crate is pushed vertically as well as horizontally when the crate is pushed horizontally, whether it slides or not even when no pushing occurs
when the crate is pushed horizontally, whether it slides or not
When two vehicles collide, momentum is conserved _______. View Available Hint(s)for Part A whether the collision is elastic or inelastic if the collision is inelastic only if deformation of either vehicle doesn't occur if the collision is elastic
whether the collision is elastic or inelastic
Recoil is noticeable if we throw a heavy ball while standing on roller skates. If instead we go through the motions of throwing the ball but hold onto it, our net recoil will be zero. small, but noticeable. the same as before.
zero
When a falling object has reached its terminal velocity, its acceleration is g. constant. zero.
zero
an object in equalilibrum is an object with a net force of
zero
The distance between the Earth and the Sun is approximately _______. 150,000 m 110 Moon diameters 110 Sun diameters twice the distance between the Earth and the Moon
110 Sun diameters
A kilogram is about
2.5 pounds
How much support force acts on a 200-N girl standing on a weighing scale? No support force unless she stands on the floor Less than 200 N 200 N More than 200 N
200n
A cart is pushed to the right with a force of 15 N while being pulled to the left with a force of 20 N. The net force on the cart is 5 N to the left. 5 N to the right. 35 N to the left. 35 N to the right.
5 N to the left. Two forces are in opposite directions, so they subtract. The direction is determined by the direction of the larger force.
If you pull on a box with 10 N to the right and a friend pulls oppositely with 5 N to the left, the net force is
5 N to the right.
The average speed of driving 30 km in 1 hour is the same as the average speed of driving 30 km in 1/2 hour. 30 km in 2 hours. 60 km in 1/2 hour. 60 km in 2 hours.
60 km in 2 hours
Friction
A force that opposes motion between two surfaces that are in contact (things rub on each other)
which of these is a scientific hypothesis? a- atoms of are smallest particles of matter b- the universe is surrounded by a second universe the existence of which cannot be detected by scientist c- Albert Einstein was the greatest physicist of the 1900's.
A is scientific because there is a test for its wrongness b has no test for possible wrongness and therefore is unscientific c is an assertion that has not test for possible wrongness.
Galileo's Law of Inertia (later Newton's first Law of Motion):
An object at rest (stopped) stays at rest. An object that is moving, keeps moving, in a straight line, at a constant rate, forever, unless a force pushes or pulls it, speeding it up or slowing it down. Here on Earth, gravity and friction constantly push and pull objects. Gravity force pulls things down faster. Friction force drags them slower.
Galileo did a lot of experiments with ramps. He found that:
Balls rolling on downward-sloping planes picked up speed. Balls rolling on upward-sloping planes lost speed. So a ball on a horizontal plane must maintain speed forever. If the ball comes to rest, it is not due to its "nature," but due to friction, a force.
Consider the video demonstration that you just watched. ( a ball moving around a half circle to hit the middle can rather than continuing in a circle and hitting the green can) Which of the following changes would make it more likely for the ball to hit both the white can and the green can?
By Newton's first law, after it has left the circular track, the ball will travel in a straight line until it is subject to a nonzero net force. Thus, the ball can only hit the white can, because that is the only can in the ball's straight-line path.
The use of inclined planes for Galileo's experiments helped him to eliminate the acceleration of free fall. discover the concept of energy. discover the property called inertia. discover the concept of momentum.
Comment: Note that inertia is a property of matter, not a reason for the behavior of matter.
Speed
Defined as the distance covered per amount of travel time. Units are meters per second. In equation form: speed= distance/time example- a girl runs 4 meters in 2 seconds 4/2=2m/s
mechanical equilibrium formula
EF=0 (e is a sideways m) (m) stands for the sumof f standers for forces for a suspended object at rest the forces acting downward The vector sum equal zero.
things that are in balance with each other illustrate
Equilibriium
Balanced forces are called
Equilibrium
If you fall off a table, you see the gravity effect: you fall, downward, speeding up (accelerating). But when you hit the floor, you slow down and come to rest. why?
Gravity is still there, pulling you down, but you don't go anywhere. Something must be pushing you up to balance. The up force comes from the floor, as a support force. Together, when the gravity (weight) force and the support force are the same size but opposite directions, the net force is zero and equilibrium is reached.
What did Galileo demonstrate in his Leaning Tower of Pisa experiment? He demonstrated that air resistance has no effect on falling objects. He demonstrated that heavy objects fall faster than light objects. He demonstrated that the forces on falling objects are the same. He demonstrated that light and heavy objects gain the same amount of speed when falling.
He demonstrated that light and heavy objects gain the same amount of speed when falling.
What was the greatest discovery by Galileo during his inclined-plane experiments? He discovered that a ball rolling down an incline and onto a horizontal surface would roll indefinitely. He discovered that heavy objects roll faster than light objects on an incline. He discovered that balls rolling down an incline gain speed, and balls rolling up an incline lose speed. He discovered that light and heavy objects gain the same speed when rolling on inclines.
He discovered that a ball rolling down an incline and onto a horizontal surface would roll indefinitely.
The Equilibrium Rule
If an object is at rest or moving at constant speed (non-accelerating), the vector sum of forces acting on the object equals zero. In equation form: ΣF = 0.
Instantaneous Speed
Instantaneous speed is the speed at any instant. Example: When you ride in your car, you may speed up and slow down. Your instantaneous speed is given by your speedometer.
A vector quantity:
Is a quantity whose description includes both magnitude (how much) and direction (which way) can be represented by arrows drawn to scale, called vectors length of arrow represents magnitude arrowhead direction shows vector direction Examples of vectors: force, velocity, acceleration
violent motion (Aristotle)
Produced by external pushes or pulls on objects. Example: Wind imposes motion on ships. Aristotle's ideas were taken as truth for well over 1000 years.
natural motion (Aristotle)
Straight up or straight down for all things on Earth. Beyond Earth, motion is circular. Example: The Sun and Moon continually circle Earth. Every object in the universe has a proper place determined by a combination of four elements: earth, water, air, and fire. Any object not in its proper place will strive to get there. Examples: Stones fall. Puffs of smoke rise.
Dr. Hewitt has clay "blobs" hanging on either side of his head in this video. When he turns around, what happens to the blobs? The blobs turn around in the same direction as Dr. Hewitt. The blobs fall off Dr. Hewitt's head. The blobs turn around in the opposite direction from Dr. Hewitt. The blobs tend to stay where they were. why?
The blobs tend to stay where they are because objects at rest tend to stay at rest unless acted upon.
Average Speed
The entire distance covered divided by the total travel time Doesn't indicate various instantaneous speeds along the way. In equation form: average speed= total distance covered/time interval example- drive a distance of 200 km in 2 hours and your average speed is 100km/h even though you may have stopped at red lights and raced through yellow ones.
Physics is about the
The nature of basic things such as motion, forces, energy, matter, heat, sound, light, and the composition of atoms.
Some alphabet letters are floating in a bowl of soup. You want to move a letter that is far away from you closer to you. How could you rotate the bowl to do that? Rotate the bowl either clockwise or counterclockwise, depending on where the letter is located. Rotate the bowl clockwise. Unfortunately, neither rotating the bowl clockwise nor rotating it counterclockwise will work. Rotate the bowl counterclockwise. why
Unfortunately, neither rotating the bowl clockwise nor rotating it counterclockwise will work. They have inertia- the tendency of an object at rest to stay at rest.
You tell your friend about the neat tablecloth trick that Dr. Hewitt demonstrated. Your friend tries to repeat this trick at home and later complains to you that it failed. Which of the following is most likely the reason that it failed? Your friend is too clumsy. The items placed on the tablecloth were too light. Your friend pulled the tablecloth too quickly. Your friend pulled the tablecloth too slowly.
Your friend pulled the tablecloth too slowly.
In science a fact
a close agreement by competent observers who make a series of observations of the same phenomenon.
Newton said that something was needed to change the motion of an object. A clear reading of his first law tells us that what is needed is _______. a non-zero net force no force at all a force a net force
a non zero net force
dynamic equilibrium
a state of balance between continuing processes example- hockey puck sliding at constant speed on slippery ice.
A theory in science is _______ an educated guess a synthesis of well-tested ideas an agreement between trained investigators forever true
a synthesis of well-tested ideas
an object in motion stays in a constant straight line motion unless
acted upon by a force. forces cause motion to change
Hang from a pair of gym rings and the upward support forces of the rings will always add up to equal your weight. each be half your weight .each equal your weight.
add up to equal your weight
The difference between Galileo and Newtons methods and Aristotelian methods is the
additional steps of testing and predictions. which created the scientific method. locks science to a set of rules and methodology helps certainty on what can be defined as facts
A truly educated person is knowledgeable about science. the arts. religion .all of these
all of these
A force of some kind is always required to
change the motion of an object (accelerate it).
Acceleration is
changing the motion, speeding up OR slowing down (OR turning).
The universe is mostly
empty space (pale blue dot)
fundamental field forces
gravity, electromagnetic, strong nuclear, weak nuclear.
what two forces dominate earth
gravity, fricton
Equations in conceptual physics are used mainly as _______.
guides to thinking
In science, an educated guess is a theory. hypothesis .both of these
hypothesis
If, while riding in a smooth-riding train, you toss a coin upward, the coin will normally land _______. in front of you in your hand in back of you off to the side of you
in your hand
(Galileo) When there are no forces (such as gravity and friction) present, such as out in space, ______ dominates
inertia
If your automobile runs out of fuel while you are driving, the engine stops but you do not come to an abrupt stop. The concept that most explains why is inertia. gravity .acceleration. resistance.
inertia
Inertia
is a property of matter to resist changes in motion. depends on the amount of matter in an object (its mass).
A scientific hypotheisis
is an educated guess that is not fully accepted until demonstrated by experiment
Einstein had interpreted mass as
it' s the effect of this objects on the space time continuum the shape of space and time Einstein says those aces wiggle and that really determine how gravity works.
when hypotheses about the relationship among natural quantities are tested over and over again and not contradicted then they may become
laws or principles.
the basic physical quantities are described as
length, time, mass, electric, current, temperature, and the amount of a substance and luminous intensity.
more mass=
more weight
physics is about the nature of basic things such as
motion, forces, energy, matter, heat, sound, light, and the composition of atoms
The net force on an object changes its
motion.
Nicolaus Copernicus proposed that earth was
moving
The combination of all forces acting on an object is called the
net force
The scientific unit of force is
newton expressed as N
equilibrium can mean ___ forces at all acting or it can mean _____ forces with some opposing each other adding up to zero.
no, many
Sometimes more than one force pushes an object, but it only has ____ amount of acceleration.
one
The scientific method of Galileo and Bacon is _______.
one of many ways of making discoveries
The earth is jam packed with
particles and masses
Weight force
pull of gravity on mass, the weight force is balanced by the support force for a foot at rest
Galileo's interpretation of motion differed from Aristotle's in that Galileo emphasized rates of time .the acceleration of free fall. the role of distance in describing motion .none of the above
rates of time
Scientific Method
recognizing a problem making a hypothesis about the answer then predicting the consequences of the hypotheses performing experiments to test predicting and formulating the simplest general rule the organizes the main ingredients.
Motion of objects is always ______ to something else example
relative, you walk on a road on earth but earth is moving relative to the sun.
Galileo's use of inclined planes allowed him to effectively slow down the acceleration of free fall. increase the acceleration beyond that of free fall. eliminate friction .eliminate the acceleration of free fall.
slow down the acceleration of a free fall
a book lying on a table compresses atoms in the table they squeeze upward on the book the compressed atoms produce the
support force
Sort each by whether they are testable by science or not Mars once had liquid water on its surface.- Earth orbits the Sun every 365.25 days.- Hurricane Katrina was an act of God.- Vince Young is the greatest quarterback of all time.People born under the sign of Sagittarius are twice as likely to be teachers as anyone else.- There will be a solar eclipse next Tuesday at 11 a.m.- Bacteria acquire resistance to antibiotics through changes in their DNA.
testable by science Mars once had liquid water on its surface.- Earth orbits the Sun every 365.25 days.- People born under the sign of Sagittarius are twice as likely to be teachers as anyone else.- There will be a solar eclipse next Tuesday at 11 a.m.- Bacteria acquire resistance to antibiotics through changes in their DNA. not testable by science- Hurricane Katrina was an act of God.- Vince Young is the greatest quarterback of all time.
When Dr. Hewitt pulls the tablecloth, what happens to the items on the tablecloth? They move horizontally in the same direction as the tablecloth. They tend to stay where they were. They move horizontally in the opposite direction from the tablecloth. They move vertically upward. When Dr. Hewitt pulls the tablecloth, why do the items on the tablecloth do what they do?
they tend to stay where they are Their inertia is sufficient to keep them there.
A scientific hypothesis deemed valid must have a test for proving it _______. wrong more than one time correct None of these choices is correct.
wrong
A scientific hypothesis may turn out to be right or it may turn out to be wrong. If it is a valid hypothesis, there must be a test for proving it right. wrong.
wrong
What is the net force on a crate sliding at an unchanging speed when pushed with a steady force of 75 N? Zero Slightly more than 75N 75 N Somewhat less than 75 N
zero
