PHYSIC 100: Exam #2
Which of the following quantities represent mass?
0.34 g 120 kg
What is the mass density of water? What is the weight density of water?
1000 kg/m3; 9800 N/m3
Which of the following quantities would be acceptable representations of weight?
12.0 lbs 1600 kN 899 MN
A force of 50 N is applied to the end of a lever, which is moved a certain distance. If the other end of the lever moves one-third as far, how much force does it exert?
150 N
What is the number of orbiting electrons in each when the isotopes are electrically neutral?
27, 27
What does the strength of a person's arm usually depend on?
The cross-sectional area
Inertia depends on mass; rotational inertia depends on mass and something else. What?
The distribution of mass ABOUT the axis of rotation
Which is easier to get swinging: a baseball bat held at the narrow end or a bat held closer to the massive end (choked up)? Also answer for a short bat versus a long bat.
The easiest is choked up and a short bat.
Why is a black hole invisible?
The escape velocity of the black hole is greater than the speed of light.
How does the force of gravity between two bodies change when the distance between them is doubled?
The force decreases to ¼ of its initial value.
After the discovery of Uranus, astronomers calculated its orbit and predicted its position in the sky using Kepler's laws of planetary motion, which had been known since the early 17th century. However, they soon discovered a small discrepancy between the predicted and actual positions of Uranus. As a scientist, what should you do when presented with such a conflict between prediction and observation?
verify that your observations are correct think about what else might cause the observed discrepancy consider that Uranus may not be a planet consider whether Kepler's laws need to be modified to account for the new observations
Quantity of space an object occupies
volume
Force on a body due to the gravitational attraction of another body
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?
weight only
Condition of free fall toward or around the Earth, in which an object experiences no support force (and exerts no force on a scale).
weightlessness
What does the atomic number of an element tell you about the element?
The number of protons in its nucleus
Product of the force on an object and the distance through which the object is moved (when force is constant and motion is in a straight line in the direction of the force); measured in joules
work
WORK done on an object is equal to the KINETIC ENERGY gained by the object
work-energy theorem
Consider two planets in space that gravitationally attract each other. If the masses of both planets are doubled, and the distance between them is also doubled, then the force between them is:
zero ("none of these")
How does the rotational inertia of the rod with the mass toward the bottom compare with the rotational inertia of the mass toward the top?
The rotational inertia of the rod with the mass CLOSER TO TOP is GREATER
Why isn't cement needed between the stone blocks of an arch that has the shape of an inverted catenary?
The stones are held together by compressive forces.
What is the Newtonian synthesis?
The union of terrestrial laws and cosmic laws
Why aren't vertical columns needed to support the middle of domed stadiums, such as the Houston Astrodome?
The weight produces compression that supports the dome.
What occurs when a proton and an antiproton meet?
They annihilate each other.
Do tides depend more on the strength of gravitational pull or on the difference in strengths? Explain.
Tides depend only on the difference.
From the viewpoint of an observer in the orbiting rocket, what happens to time on the other rocket as it falls toward the event horizon of the black hole?
Time runs increasingly slower as the rocket approaches the black hole.
How do matter and antimatter differ?
When matter and antimatter meet, they annihilate in a flash of energy.
A force sets an object in motion. When the force is multiplied by the time of its application, we call the quantity impulse, and an impulse changes the momentum of that object. What do we call the quantity force multiplied by distance?
Work
What is the magnitude of the gravitational field at Earth's center?
Zero N/kg
Linking together of atoms to form larger structures, such as molecules and solids.
atomic linking
An arch in the shape of an inverted catenary
catenary arch
For a planet of uniform density, how would the magnitude of the gravitational field halfway to the center compare with the field at the surface?
g/2 m/s2
Force field that exists in the space around every mass or group of masses; measured in Newtons per kilogram
gravitational field
Energy of motion, equal (non-relativistically) to half the mass multiplied by the speed squared.
kinetic energy
What are the units of measurement for tangential speed? For rotational speed?
m/s for tangential, RPM for rotational
Substances mixed together WITHOUT combining chemically
mixture
An object that has kinetic energy must be:
moving
Tide that occurs when the moon is halfway between a new moon and a full moon, in either direction. The tides due to the sun and the moon partly cancel, so that the high tides are lower than average and the low tides are not as low as average.
neap tide
A rotating wheel has a greater rotational inertia when most of its mass is:
near rim
As the falling rocket plunges toward the event horizon, an observer in the orbiting rocket would see that the falling rocket __________.
slows down as it approaches the event horizon and never actually crosses the event horizon
Phase of matter characterized by DEFINITE volume and shape
solid
The Earth is currently accelerating toward the Sun (centripetal acceleration). If the Sun collapsed into a black hole, this acceleration would
stay the same
The reaction force applied by a stretched string, rope or a similar object on the objects that stretch it.
tension
Distinguish between linear momentum and angular momentum.
*Angular* momentum depends on *distribution* of mass *Linear* momentum depends on the *total* mass.
What is the volume of a sugar cube that measures 1 cm on each side? What is the cross-sectional area of the cube? The total surface area?
1 cm3, 1 cm2, 6 cm2
What is the ratio of escape speed from Earth to circular orbital speed? Ignore air resistance.
1.41
What is the magnitude of Earth's gravitational force on a 1-kg body at Earth's surface?
10 N
What will the kinetic energy of a pile driver ram be if it starts from rest and undergoes a 10 kJ decrease in potential energy?
10 kj
A projectile is launched vertically at 100 m/s. If air resistance can be ignored, at what speed will it return to its initial level?
100 m/s
What is the efficiency of a machine that miraculously converts all the input energy to useful output energy?
100%
A projectile is launched upward at an angle of 70° from the horizontal and strikes the ground a certain distance downrange. For what other angle of launch at the same speed would this projectile land just as far away?
20 degrees
The atomic masses of two isotopes of cobalt are 59 and 60. What is the number of PROTONS in each?
27, 27
The atomic masses of two isotopes of cobalt are 59 and 60. What is the number of NEUTRONS in each?
32, 33
If you push an object twice as far while applying twice the force you do:
4x as much
A projectile falls beneath the straight-line path it would follow if there were no gravity. How many meters does it fall below this line if it has been traveling for 1 s? For 2 s?
5 m, 20 m
How far does a projectile drop in 1 second? What is the speed needed for a projectile to orbit Earth?
5 m, 8 km/s
If a 1-kg object stretches a spring by 2 cm, then how much will the spring be stretched when it supports a 3-kg object? (Assume the spring does not reach its elastic limit.)
6 cm
If an input of 100 J in a pulley system increases the potential energy of a load by 60 J, what is the efficiency of the system?
60 %
How many shells are represented in the presently known periodic table?
7
How do you explain the saying "The bigger they are, the harder they fall" using scaling?
A BIG CREATURE has a SMALL RATIO of surface area to mass, so air resistance doesn't slow it as much when it falls.
Can a horizontal I-beam support a greater load when the web is horizontal or when the web is vertical? Explain.
A horizontal I-beam is stronger when the web is vertical because most of the material is where it is needed for the most strength, in the top and bottom flanges. When supporting a load, one flange will be under tension and the other flange under compression. But when the web is horizontal, only the edges of the flanges, much smaller than the flanges themselves, play these important roles.
What is the purpose of a model in science?
A model is an abstraction that helps us visualize and predict.
How does a molecule differ from an atom? Give an example.
A molecule is composed of two or more atoms bonded together: H2O.
Why can small creatures fall considerable distances without injury, while people need parachutes to do the same?
A small creature has greater surface area per unit mass, so air resistance slows it more when it falls.
What is the relationship between the center of gravity and the support base for an object that is in stable equilibrium?
A vertical line through the center of gravity must pass inside the support base of the object.
Why can't you stand with your heels and back to a wall and then bend over to touch your toes and return to your stand-up position?
A vertical line through the center of gravity of your body is in front of the tips of your toes, which is outside your support base.
Why doesn't the Leaning Tower of Pisa topple over?
A vertical line through the center of gravity passes inside its support base.
Your friend says that what makes one element distinct from another is the number of electrons about the atomic nucleus. Do you agree wholeheartedly, partially, or not at all? Explain.
Agree partially. It's better to say an element is defined by the number of protons in the nucleus. The number of protons and electrons are equal only when the element is not ionized.
Who first explained Brownian motion and made a convincing case for the existence of atoms?
Albert Einstein
How can a projectile "fall around the Earth"? The projectile falls 5 m for every 8 km and so does Earth. A projectile can "fall around Earth" if the distance it falls matches the curvature of Earth. In a circular orbit around a spherical planet, the force and the fall are always toward the center. All of the above.
All
How can gravity be simulated in an orbiting space station? a. Spin a station shaped like a bicycle wheel b. Spin two pods connected by a cable c. Rotate a cylinder to create centrifugal force as viewed by a person on the inside of the curved outer wall d.All of the above
All of the above
What did Newton discover about gravity? The Newtonian synthesis The law of universal gravitation The equation for the force of gravity All of the above
All of the above
What exactly is a projectile?
An object that is projected by some means and continues in motion by its own inertia.
Product of a body's rotational inertia and rotational velocity about a particular axis. For an object that is small compared with the radial distance, it is the product of mass, speed, and radial distance of rotation. Product of mass of an object and its linear velocity
Angular momentum
What is the law of inertia for rotating systems in terms of angular momentum?
Angular momentum does not change without an applied external torque.
Inside a freely-falling runaway elevator, your:
Apparent weight is zero
Number associated with an atom, equal to the number of protons in the nucleus, or, equivalently, to the number of electrons in the electron cloud of a neutral atom.
Atomic number
How does the arrangement of atoms in a crystalline substance differ from the arrangement in a noncrystalline (amorphous) substance?
Atoms in *crystals* are in an *ordered* array. In *amorphous* materials, they are *randomly* distributed.
What is a mixture? Cite two examples.
Atoms pressed together WITHOUT BONDING : air and salt and sand
Consider three axes of rotation for a pencil: along the lead, at right angles to the lead at the middle, and at right angles to the lead at one end. Rate the rotational inertias about each axis from smallest to largest.
Axis along the lead, through the center, through one end
The crew of a cargo plane wishes to drop a crate of supplies on a target below. To hit the target, when should the crew drop the crate? Ignore air resistance.
Before the plane is directly over the target
Why does bending your legs when running enable you to swing your legs to and fro more rapidly?
Bending your legs shortens them, thus reducing rotational inertia.
Is the sum of kinetic and potential energies a constant for satellites in circular orbits, in elliptical orbits, or in both?
Both
2 balls from ladder, one dropper, the other thrown horizontally....which one lands first?
Both at same time
Two golfers each hit a ball at the same speed, but one at 60 ∘ with the horizontal and the other at 30 ∘. Which ball goes farther? Which hits the ground first? (Ignore air resistance.)
Both balls have the same range. The ball with the initial projection angle of 30 degrees, however, is in the air for a shorter time and hits the ground first.
Who gathered the data that showed planets traveling in elliptical paths around the Sun? Who discovered elliptical orbits? Who explained them?
Brahe, Kepler, Newton
If you want to light some wood on fire, what would most likely make the wood light, and why?
Breaking the log down into small pieces of wood will increase the amount of wood surface that can catch fire.
Haphazard movement of tiny particles suspended in a gas or liquid resulting from bombardment by the fast-moving molecules of the gas or liquid
Brownian movement
Point at the center of an object's mass distribution, where all its mass can be considered to be concentrated. For everyday conditions, it is the SAME AS CENTER OF GRAVITY
Center of mass
Apparent OUTWARD force in a rotating frame
Centrifugal force
What causes dust particles and tiny grains of soot to move with Brownian motion?
Collisions with invisible molecules
If you stopped an Earth satellite dead in its tracks, it would simply crash into Earth. Why, then, don't the communications satellites that "hover motionless" above the same spot on Earth crash into Earth?
Communication satellites only appear motionless because their orbital period coincides with the daily rotation of the Earth.
Atoms of different elements with bonds between them: NaCl and H2O
Compound
Is it tension or compression that strengthens an arch that supports a load?
Compression
The intersection of a body in 3-dimensional space with a plane. Sometimes called the cross sectional area.
Cross section
If you want to cool down a drink with ice, which of the following would make it cool faster and why?
Crushing the lump into small pieces will put more of the ice's surface area is in contact with the drink.
Why do some animals curl up into a ball when they are cold?
Curling up presents less surface area to the surroundings.
Unseen and unidentified matter that is evident by its gravitational pull on stars in the galaxies—comprising perhaps 90% of the matter of the universe.
Dark matter
The uranium atom is the heaviest and most massive atom among the naturally occurring elements. Why, then, isn't a solid bar of uranium the densest metal?
Density has not only to do with the mass of the atoms that make up a material, but with the spacing between the atoms as well. The atoms of the metal iridium, for example, are not as massive as uranium atoms, but due to their close spacing they make up the densest of the metals. Uranium atoms are not as closely spaced as iridium atoms.
If a loaf of bread is compressed:
Density increases
If a machine multiplies force by a factor of 4, what other quantity is diminished, and by how much?
Distance is diminished to one-quarter.
According to Newton, doubling the distance between two interacting objects, _____'s the gravitational force between them.
Divides by 4
A tightrope walker more easily balances on a tight wire if his pole:
Droops (lower center of mass)
If the Moon pulls Earth as strongly as Earth pulls the Moon, why doesn't Earth rotate around the Moon, or why don't both rotate around a point midway between them?
Earth and Moon do rotate around a common point, but it's not midway between them (which would require both Earth and Moon to have the same mass). The point around which Earth and Moon rotate (called the barycenter) is within the Earth about 4600 km from the Earth's center.
Earth exerts on the spaceship (place in order)
Earth---->Moon
The atoms that constitute your body are mostly empty space, and structures such as the chair you're sitting on are composed of atoms that are also mostly empty space. So why don't you fall through the chair?
Electrical repulsion. Electrons speeding around within an atom create an electrified cloud that repels the similar clouds of other electrons, preventing the atoms from coalescing and keeping us from falling through our chairs. (For the record, quantum effects play a large role as well.)
Since atoms are mostly empty space, why don't we fall through a floor we stand on?
Electrons in one atom repel the electrons in another.
Which has more skin: an elephant or a mouse? Which has more skin per unit of body weight: an elephant or a mouse?
Elephant, mouse
Which requires more food daily: an elephant or a mouse? Which requires more food per unit of body weight: an elephant or a mouse?
Elephant, mouse
The oval-shaped path followed by a satellite. For this shape, the sum of the distances from any point on the curve to two internal focal points is a constant.
Ellipse
State of balance, no net forces an no net torque
Equilibrium
Velocity that a projectile, space probe, etc., must reach to escape the gravitational influence of the Earth or celestial body to which it is attracted.
Escape speed
The factor most directly responsible for making a black hole invisible is its:
Escape velocity
During an eclipse of the Sun the ocean's tides on Earth are:
Extra high/low
Can a machine multiply input force? Input distance? Input energy?
Force and distance, but not energy
An apple falls because of the gravitational attraction to Earth. How does the gravitational attraction of Earth to the apple compare? (Does force change when you interchange m1 and m2 in the equation for gravity - m2 m1 instead of m1 m2 ?)
Force and magnitude are the same, acceleration is different
Consider the video you just watched. Suppose we replace the original launcher with one that fires the ball upward at twice the speed. We make no other changes. How far behind the cart will the ball land, compared to the distance in the original experiment?
Four times as far
You could swallow a capsule of germanium without ill effects. But, if a proton were added to each of the germanium nuclei, you would not want to swallow the capsule. Why? (Consult the periodic table in the Study Area.)
Germanium would become arsenic.
When air resistance is neglected, why does the vertical component of velocity for a projectile change with time, whereas the horizontal component of velocity doesn't change?
Gravity is a purely vertical force.
Why does the force of gravity change the speed of a satellite in an elliptical orbit?
Gravity slows the satellite as it moves away and speeds it up on its return.
At what part of an elliptical orbit does an Earth satellite have the greatest speed? The lowest speed?
Greatest nearest Earth; lowest furthest from Earth
The experimenter from the video rotates on his stool, this time holding his empty hands in his lap. You stand on a desk above him and drop a long, heavy bean bag straight down so that it lands across his lap, in his hands. What happens?
He spins slower
If a skater who is spinning pulls her arms in so as to reduce her rotational inertia by half, by how much will her angular momentum change? By how much will her rate of spin change?
Her angular momentum does not change. Her spin rate doubles.
Distance of stretch or squeeze (extension or compression) of an elastic material is directly proportional to the applied force. Where Δx is the change in length and k is the spring constant, F = k Δx.
Hooke's law
What is the most abundant element in the known universe?
Hydrogen
If a golf ball and a Ping-Pong ball both move with the same kinetic energy, can you say which has the greater speed? Explain in terms of the definition of KE. Similarly, in a gaseous mixture of heavy molecules and light molecules with the same average KE, can you say which have the greater speed?
If KEs are the same but masses differ, then the ball with smaller mass has the greater speed. That is, 1⁄2Mv^2 = 1⁄2mV^2. Likewise with molecules, where lighter ones move faster on the average than more massive ones
The spool is pulled in three ways, as shown. There is sufficient friction for rotation. In what direction will the spool roll in each case?
In all three cases the spool moves to the right.In the first case there is a torque about the point of contact with the table that rotates the spool clockwise, so the spool rolls to the right. In the second case the pull's line of action extends through (not about) the point of table contact, yielding no lever arm and therefore no torque; but with a force component to the right; hence the spool slides to the right without rolling. In the third case the torque produces clockwise rotation so the spool rolls to the right.
Where is the center of mass of a hollow soccer ball?
In the center of the ball
When you pedal a bicycle, maximum torque is produced when the pedal sprocket arms are in the horizontal position, and no torque is produced when they are in the vertical position. Explain.
In the horizontal position the lever arm equals the length of the sprocket arm, but in the vertical position, the lever arm is zero because the line of action of forces passes right through the axis of rotation. (With cycling cleats, a cyclist pedals in a circle, which means they push their feet over the top of the spoke and pull around the bottom and even pull up on the recovery. This allows torque to be applied over a greater portion of the revolution.)
How does the force needed to turn the wrench change if you increase the lever arm?
It decreases
How does the lever arm change if you decrease the angle of the force?
It decreases
How does the lever arm change when you decrease the distance to the nut?
It decreases
A stone is thrown upward at an angle. What happens to the magnitude of the vertical component of its velocity as it rises? As it falls?
It decreases while rising, but it increases while falling.
In what sense does the Moon "fall"?
It falls away from the straight path that it would follow if there were no forces acting on it.
Predict how the vertical component of the velocity will change with time after the projectile is fired.
It first decreases to zero and then increases in the opposite direction.
How does one isotope differ from another?
It has a different number of neutrons.
When the speed of a moving car is doubled, how much more kinetic energy does it have?
It has four times as much Kinetic energy = (1/2)mass X (velocity squared)
As distance increases between most of the mass of an object and its center of rotation, how does rotational inertia change?
It increases.
What happens to the strength of the gravitational field at the surface of a star that shrinks?
It increases.
What is a gravitational field, and how can its strength be measured?
It is a force field on any body with mass. Its strength is the force per unit mass on a test mass.
Is it easier for a circus performer to balance a long rod held vertically with people hanging off the other end, or the same long rod without the people at the other end, and why?
It is easier for the performer to balance a long rod held vertically with people at the other end because the rotational inertia is greater.
How does the electric charge of a proton compare with the electric charge of an electron?
It is equal and opposite.
What is meant by the "lever arm" of a torque?
It is the perpendicular distance from the rotational axis to the line along which the force acts.
How does the thickness of paint sprayed on a surface change when the sprayer is held twice as far away?
It is ¼ as thick.
Compared with a car moving at some original speed, how much work must the brakes of a car supply to stop a car that is moving twice as fast? How will the stopping distances compare?
It takes four times the work and four times the stopping distance. (Kinetic energy of car = 1/2 X mass x (change in velocity)^2 = Work to stop it = Work in Joules.)
If you toss a stick into the air, it appears to wobble all over the place. Specifically, about what place does it wobble?
It will rotate about the center of mass.
If Earth shrank, but there was no change in its mass, then what would happen to your weight at the surface?
It would increase.
From Part B, you know that from afar you'll never see the in-falling rocket cross the event horizon, yet it will still eventually disappear from view. Why?
Its light will become so redshifted that it will be undetectable.
Who advanced the idea of atoms in the early 1800s?
John Dalton
What is the unit of work?
Joule
The squares of the times of revolution (days, months, or years) of the planets are proportional to the cubes of their average distances from the sun (T2 ~ R3 for all planets).
Kepler's Third Law
What was the direction of the force on a planet in a circular orbit in Kepler's thinking? In Newton's thinking?
Kepler: Parallel Newton: Towards planet
If both sacks in the preceding question are lifted their respective distances in the same time, how does the power required for each compare? How about for the case in which the lighter sack is moved the same distance in half the time?
Lifted in the same time, the power is the same. The light sack moving in half the time requires double the power.
If the linear dimensions of an object are doubled, by how much does the surface area increase? By how much does the volume increase?
4 times, 8 times
The reason the Moon does not crash into the Earth is because the moon has...
Moon has a sufficient Tangential speed.
Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that was accelerating upward? Downward?
More compressed while accelerating upward, but less compressed while accelerating downward
Are most of the atoms around us younger or older than the Sun?
Most are older than the Sun
How is a flywheel constructed to maximize its rotational inertia?
Most of the mass is concentrated FAR FROM AXIS
Newton viewed the curving of the path of a planet as being caused by a force acting on the planet. How did Einstein view the curved path of a planet?
Moving in curved 4-dimensional space time
To change mercury into gold, a pair of protons must be: A. removed from the mercury nucleus. B. added to the mercury nucleus. C. Both of these. D. Neither of these.
Neither
What was the cause of perturbations discovered in the orbit of the planet Uranus? What later discovery did this lead to?
Neptune caused the perturbations, and later Pluto was discovered.
Do your answers to the preceding question depend on the angle at which the projectile is launched?
No
As an object slides down an inclined plane, is the normal force doing work?
No, because the normal force is perpendicular to the displacement.
Can a satellite maintain an orbit in the plane of the Arctic Circle? Why or why not?
No, for an orbit in the plane of the Arctic Circle does not intersect the Earth's center. All Earth satellites orbit in a plane that intersects the center of the Earth. A satellite may pass over the Arctic Circle, but cannot remain above it indefinitely, as a satellite can over the equator.
Would a torque on the Moon occur if the Moon were spherical, with both its center of mass and center of gravity in the same location? Why?
No. The torque requires a distance between the center of mass and the center of gravity.
Where did the heaviest elements originate?
Nuclear fusion in supernovae
What is the ultimate source of geothermal energy?
Nuclear power in Earth's interior
Why aren't high ocean tides exactly 12 hours apart?
Ocean tides are not exactly 12 hours apart because while the Earth spins, the Moon moves in its orbit and appears at its same position overhead every 25 hours, instead of every 24 hours. So the two-high-tide cycle occurs at about 25-hour intervals, making high tides about 12.5 hours apart.
Friction is needed for a car rounding a curve. But, if the road is banked, friction may not be required at all. What, then, supplies the needed centripetal force? (Hint: Consider vector components of the normal force on the car.)
On a banked road the normal force, at right angles to the road surface, has a horizontal component that provides the centripetal force. Even on a perfectly slippery surface, this component of the normal force can provide sufficient centripetal force to keep the car on the track.
Why does the force of gravity do work on a car that rolls down a hill but no work when it rolls along a level part of the road?
On the hill there is a component of gravitational force in the direction of the car's motion. This component of force does work on the car. But on the level, there is no component of gravitational force along the direction of the car's motion, so the force of gravity does no work in this case.
Which moves faster in m/s on a merry-go-round: a horse near the inside or a horse on the outside near the outer rail?
Outside (larger circumference compared to inside)
The TANGENITAL VELOCIY of an Earth satellite is its velocity
Parallel
Which planet should Punch travel to if his goal is to weigh in at 118 lb? Refer to the table of planetary masses and radii given to determine your answer.
Pentune
Silicon is the chief ingredient of both glass and semiconductor devices, yet the physical properties of glass are different from those of semiconductor devices. Explain.
Physical properties vary for each of these.The silicon in glass is amorphous, whereas in semiconductors it is crystalline. Silicon in sand, from which glass is made, is bound to oxygen as silicon dioxide, while that in SEMICONDUCTOR IS ELEMENTAL and extremely pure. Hence their physical properties differ.
Branch of physics concerned with the microworld based on wave functions and probabilities, where many quantities are granular (in units called quanta), rather than continuous, and where particles of light (photons) and particles of matter (such as electrons) exhibit wave as well as particle properties. Sometimes referred to as quantum physics or quantum theory.
Quantum physics
A stone is thrown upward at an angle. What happens to the horizontal component of its velocity as it rises? As it falls?
Rising or falling, it does not change.
For which angle is the range a maximum (with the initial speed held constant)?
45
The front wheels of a racing vehicle are located far out in front to help keep the vehicle from nosing upward when it accelerates. What physics concepts play a role here?
Rotational inertia and torque are most predominantly illustrated here, and the conservation of angular momentum also plays a role.
How does speed affect the friction between a road and a skidding tire?
Speed has no effect on the friction.
Which has the higher tides: spring tides or neap tides? Why?
Spring tides are higher, because the tides from the Moon and Sun add together.
State of an object balanced so that any small displacement or rotation raises its center of gravity.
Stable equilibrium
What is the advantage to a gymnast of being short in stature?
Strength varies in approximate proportion to the cross-sectional area of arms and legs (proportional to the square of the linear dimensions). Weight varies in proportion to the volume of the body (proportional to the cube of the linear dimension). So—other things being equal—the *ratio of strength to weight is greater for smaller persons*.
What is Hooke's law? Does it apply to elastic materials or to inelastic materials?
Stretch is proportional to force for elastic materials.
Linear speed along a curved path
Tangential speed
On a rotating turntable, how do tangential speed and rotational speed vary with distance from the center?
Tangential speed increases with distance. Rotational speed is constant.
If the acceleration due to gravity on the earth is 9.8 m/s2, what is the acceleration due to gravity on Rams?
5.7 m/s^2
At what point in its motion is the KE of a pendulum bob at a maximum? At what point is its PE at a maximum? When its KE is at half its maximum value, how much PE does it have relative to its PE at the center of the swing?
The KE of a pendulum bob is maximum where it moves fastest, at the lowest point; PE is maximum at the uppermost points. When the pendulum bob swings by the point that marks half its maximum height, it has half its maximum KE, and its PE is halfway between its minimum and maximum values. If we define PE = 0 at the bottom of the swing, the place where KE is half its maximum value is also the place where PE is half its maximum value, and KE = PE at this point. (By energy conservation: Total energy = KE + PE.)
Why aren't heavier elements much larger than lighter elements?
The LARGER POSITIVE charge in the nucleus PULLS ELECTRONS into closer orbits.
Since the Moon is gravitationally attracted to Earth, why doesn't it simply crash into Earth?
The Moon's tangential velocity is what keeps the Moon coasting around the Earth rather than crashing into it. If its tangential velocity were reduced to zero, then it would fall straight into the Earth!
Why does the gravity in the Space Shuttle compare with the gravity on Earth the way it does?
The Space Shuttle is about the same distance from the center of the Earth than from the surface of the Earth.
Why do the astronauts in the Space Shuttle float around?
The Space Shuttle is in free fall, so the shuttle and the astronauts inside it are continuously falling toward the Earth. They thus experience apparent weightlessness.
What is the ultimate source of the energy from fossil fuels, dams, and windmills?
The Sun
Describe how the gravitational forces from the Sun and the Moon compare from one side of Earth to the other.
The Sun exerts a stronger force on the side of Earth nearest the Sun, and the Moon exerts a stronger force on the side nearest the Moon.
Why can atoms be seen with an electron beam?
The WAVELENGTH of the electrons is SMALLER than an atom.
Somebody told your friend that if an antimatter alien ever set foot upon Earth, the whole world would explode into pure radiant energy. Your friend looks to you for verification or refutation of this claim. What do you say?
The amount of matter that a given amount of antimatter would annihilate is the same as the amount of antimatter, a pair of particles at a time. The whole world could not be annihilated by antimatter unless the mass of antimatter were at least equal to the mass of the world.
Where were the atoms that make up a newborn infant "manufactured"?
The atoms that make up a newborn baby or anything else in this world originated in the explosions of ancient stars. The molecules that make up the baby, however, were formed from atoms ingested by the mother and transferred to her womb.
Which ball (if either) has the greatest speed at the moment of impact?
The ball thrown horizontally
How would the result of this experiment change if we replaced the ball with another one that had half the mass? Ignore air resistance
The ball would still land in the cart.
How does the range of the object change if its initial velocity is tripled (keeping the angle fixed and less than
The ball's range is nine times as far.
Two cars are raised to the same elevation on service-station lifts. If one car is twice as massive as the other, compare their gains of potential energy.
The car with twice the mass has twice the gain of potential energy.
Where is the center of mass of a baseball? Where is its center of gravity?
The center of mass and the center of gravity are both at the center of the spherical ball.
If you place a Styrofoam cup on the table and a bunch of BBs move around it randomly, what will happen to the cup, and why?
The cup will move randomly in different directions because the BBs will exert unequal forces on the cup in different directions.
As you found in Part A, your weight will be greater than normal when the elevator is moving upward with increasing speed. For what other motion would your weight also be greater than your normal weight?
The elevator moves downward while slowing in speed.
What is the magnitude of the gravitational force between two 1-kg bodies that are 1 m apart?
6.67 × 10 ^-11 N (Newtons is they key term)
Why doesn't the force of gravity change the speed of a bowling ball as it rolls along a bowling lane?
The force is at a right angle to the motion. *BOWLING LANE, RIGHT ANGLE*
Why doesn't the force of gravity change the speed of a satellite in circular orbit?
The force is at a right angle to the velocity.
Is it an inward force or an outward force that is exerted on the clothes during the spin cycle of an automatic washing machine? What about the direction of the force on the water?
The force is inward on clothes and there is none on water.
State Newton's law of universal gravitation in words. Then do the same with one equation.
The force is proportional to the product of two masses and inversely proportional to the square of the distance between their centers: F ~ m1m2/d2.
Why is kinetic energy a constant for a satellite in a circular orbit but not for a satellite in an elliptical orbit?
The force of gravity is PERPENDICULAR to the motion IN A CIRCULAR orbit but not in an elliptical orbit.
Most people today know that the ocean tides are caused principally by the gravitational influence of the Moon, and most people therefore think that the gravitational pull of the Moon on Earth is greater than the gravitational pull of the Sun on Earth. What do you think?
The gravitational pull of the Sun on the Earth is greater than the gravitational pull of the Moon. The tides, however, are caused by the differences in gravitational forces by the Moon on opposite sides of the Earth. The difference in gravitational forces by the Moon on opposite sides of the Earth is greater than the corresponding difference in forces by the stronger pulling but much more distant Sun.
How does the gravity in the Space Shuttle compare with the gravity on Earth's surface?
The gravity in the Space Shuttle is approximately equal to the gravity on the surface of the Earth.
Iridium is not the heaviest atom found in nature. What, then, accounts for a chunk of pure iridium being the densest substance on Earth?
The iridium atoms are closer together in the crystalline form.
What and where is the neutral layer in a beam that supports a load?
The layer in which there is neither tension nor compression along the middle from end to end
Explain why a long pole is more beneficial to a tightrope walker if the pole droops.
The long drooping pole lowers the CG of the balanced system—the tightrope walker and the pole. The rotational inertia of the pole contributes to the stability of the system also.
Which of the following items would remain without rusting longer: a solid lump of steel, or steel wool that weighs the same amount?
The lump of steel would stay without rusting longer, because not as much of it comes in contact with the air.
How does the approximate number of atoms in the air in your lungs compare with the number of breaths of air in Earth's atmosphere?
The numbers are the about the same, 10^23.
Why did the particles jiggle around?
The particles were struck by atoms, but unequally on different sides.
For orbits of greater altitude, is the period longer or shorter? Is the speed faster or slower?
The period is longer and the speed is slower.
What did Kepler discover about the periods of planets and their distances from the Sun?
The period squared was proportional to the distance cubed.
Gravitational force acts on all bodies in proportion to their masses. Why, then, doesn't a heavy body fall faster than a light body?
The reason that a heavy body doesn't fall faster than a light body is because the greater gravitational force on the heavier body (its weight), acts on a correspondingly greater mass (inertia). The ratio of gravitational force to mass is the same for every body—hence all bodies in free fall accelerate equally. And it's true not just near the Earth, but anywhere.
Compared with the energy it takes to separate oxygen and hydrogen from water, how much energy is released when they recombine?
The same amount of energy is released when they recombine.
At which of the indicated positions does the satellite in elliptical orbit experience the greatest gravitational force? Have the greatest speed? The greatest velocity? The greatest momentum? The greatest kinetic energy? The greatest gravitational potential energy? The greatest total energy? The greatest angular momentum? The greatest acceleration?
The satellite experiences the greatest gravitational force at A (far left of the circle), where it is closest to the Earth The perigee; and the greatest speed and the greatest velocity at A, and by the same token the greatest momentum and greatest kinetic energy at A, The greatest gravitational potential energy at the farthest point C. It would have the same total energy (KE + PE) at all parts of its orbit, likewise the same angular momentum because it's conserved. It would have the greatest acceleration at A, where F/m is greatest.
When Dr. Hewitt cuts the broom right through the center of gravity, how do the weights of the two sides of the broom compare?
The shorter side, where the bristles of the broom are, has a greater weight than the handle.
How does the tapered rim of a wheel on a railroad train allow one part of the rim to have a greater tangential speed than another part when it is rolling on a track?
The tangential speed is proportional to the radius. The inside of the wheel rolls on a larger radius than the outside of the wheel.
A tapered cup rolled on a flat surface makes a circular path. What does this tell you about the tangential speed of the rim of the wide end of the cup compared with that of the rim of the narrow end?
The tangential speed of the wide end is faster.
How does the torque due to the weight of one side of the broom exerted around the balance point compare with the torque exerted by the weight of the other side of the broom around the balance point?
The torque due to the weight of the shorter side (the bristles of the broom) is equal in magnitude to the torque due to the weight of the longer side, and opposite in direction.
Predict how the upward force exerted on the feet by the scale will compare to the man's weight if the elevator is moving downward at a CONSTANT speed.
The upward force on the feet will be equal to the man's weight.
Predict how the upward force exerted on the feet by the scale will compare to the weight of the man if the elevator is moving upward at a constant speed.
The upward force on the feet will be equal to the man's weight.
Predict how the upward force exerted on the feet by the scale will compare to the man's weight if the elevator is accelerating downward.
The upward force on the feet will be less than the man's weight.
Predict how the upward force exerted on the feet by the scale will compare to the man's weight if the elevator is accelerating upward.
The upward force on the feet will exceed the man's weight.
Why do French fries cook faster when they are cut into thinner pieces, and why do meatballs cook faster when they are flattened?
There is a GREATER SURFACE AREA for the SAME AMOUNT OF FOOD in the thinner fries and flattened meatballs.
Explain why a centripetal force does not do work on a circularly moving object.
There is no component of force parallel to the direction of motion, which work requires.
If you are not wearing a seat belt in a car that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: centripetal, centrifugal, or no force?
There is no force as viewed by someone outside the car. To them you move in a straight line.
Would the springs inside a bathroom scale be more compressed or less compressed if you weighed yourself in an elevator that was moving upward at constant velocity? Downward at constant velocity?
There would be no more compression and no more expansion for both upward and downward motion.
What is the source of energy in sunshine?
Thermonuclear fusion energy
How do clockwise and counterclockwise torques compare when a system is balanced?
They are equal in magnitude and opposite in direction.
Why are occupants of the International Space Station weightless?
They are in free fall.
Which is denser: an object that has a density of 1000 kg/m3 or one that has a density of 1 g/cm3?
They are the same density.
Why is it important that the projectile in the preceding question be 100 km or higher above Earth?
To avoid air resistance
Why are the cross-sections of metal beams in the shape of the letter I instead of solid rectangles?
To reduce the weight of the beam while preserving the resistance to bending
What does a torque tend to do to an object?
Torque tends to twist or change the state of rotation of the object.
When you whirl a can at the end of a string in a circular path, what is the direction of the force you exert on the can?
Toward the center of the circle
If the rotational speed of a turntable is doubled, then the linear speed of a speck of dust can remain the same if the speck is moved:
Towards center
An object is lifted to a given height. A second, identical object is lifted to twice the height. Compared to the first object, the second has how many times the gravitational potential energy.
Twice
A rock is thrown upward at 50 degrees with respect to the horizontal. As it rises, its HORIZONTAL component of velocity
Unchanged
When a rifle with a longer barrel is fired, the force of expanding gases acts on the bullet for a longer distance. What effect does this have on the velocity of the emerging bullet? (Do you see why long-range cannons have such long barrels?)
When a rifle with a long barrel is fired, more work is done as the bullet is pushed through the longer distance. A greater KE is the result of the greater work, so of course, the bullet emerges with a greater velocity. (Note that the force acting on the bullet is not constant, but decreases with increasing distance inside the barrel.)
Why do we say that a blob of putty is inelastic?
When deformed, it does not return to its original shape.
Why do we say that a spring is elastic?
When deformed, it returns to its original shape.
When is the potential energy of something significant?
When the potential energy changes
When G was first measured by Henry Cavendish, newspapers of the time hailed his experiment as the "weighing Earth experiment." Why?
With a known mass, a scale, and the radius of Earth, you can calculate the unknown mass of Earth if you know G.
Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in the orbiting space shuttle do not. This is because passengers in the space shuttle are
Without support forces
Two people who weigh the same climb a flight of stairs. The first person climbs the stairs in 30 s, and the second person climbs them in 40 s. Which person does more work? Which uses more power?
Work done by each is the same, for they reach the same height. The one who climbs in 30 s uses more power because work is done in a shorter time.
What evidence can you cite for the microscopic crystal nature of certain solids? For the macroscopic crystal nature?
X-ray diffraction and the macroscopic shape of crystals
Do tides occur in the molten interior of Earth for the same reason that tides occur in the oceans?
Yes, due to the difference in gravitational force ACROSS the core
When the space shuttle coasts in a circular orbit at constant speed about Earth, is it accelerating? If so, in what direction? If not, why not?
Yes, the shuttle is accelerating, as evidenced by its continual CHANGE OF DIRECTION It accelerates due to the gravitational force between it and the Earth. The ACCELERATION IS TOWARDS EARTH'S CENTER
Suppose that you and two classmates are discussing the design of a roller coaster. One classmate says that each summit must be lower than the previous one. Your other classmate says this is nonsense, for as long as the first one is the highest, it doesn't matter what height the others are. What do you say?
You agree with your second classmate. The coaster could just as well encounter a low summit before or after a higher one, so long as the higher one is enough lower than the initial summit to compensate for energy dissipation by friction.
Your friend says that the primary reason astronauts in orbit feel weightless is that they are beyond the main pull of Earth's gravity. Why do you agree or disagree?
You disagree, for the force of gravity on orbiting astronauts is almost as strong as at Earth's surface. They feel weightless because of the absence of a support force.
Where do you weigh more: at the bottom of Death Valley or atop one of the peaks of the Sierra Nevada? Why?
You weigh more in Death Valley because you are closer to the center of Earth.
Give an example of when your weight is greater than mg. Give an example of when your weight is zero.
Your weight is greater than mg when you are accelerating upward. Your weight is zero when you are in free fall.
How much work is done on a satellite in a circular orbit about Earth?
Zero
What would the magnitude of the gravitational field be anywhere inside a hollow, spherical planet?
Zero N/kg
If you push a crate horizontally with 100 N across a 10-m factory floor and the friction between the crate and the floor is a steady 70 N, how much kinetic energy does the crate gain?
a) You do F d = 100 N 10 m = 1000 J of work. (b) Because of friction, net work on the crate is less. KE = net work = net force distance = (100 N - 70 N)(10 m) = 300 J
The famous Leaning Tower of Pisa doesn't topple over because its center of gravity is:
above a place of support
If you were inside the rocket that falls toward the event horizon, from your own viewpoint you would __________.
accelerate as you fall and cross the event horizon completely unhindered
The amount of gravitational force that acts on the space shuttle while in orbit is:
almost as much as the shuttle's weight on the Earth's surface.
Matter composed of atoms with negative nuclei and positive electrons
antimatter
A curved structure capable of spanning a space while supporting significant weight
arch
A physical quantity expressing the *size of a part of a surface*
area
The following five diagrams show pairs of astronomical objects that are all separated by the same distance d. Assume the asteroids are all identical and relatively small, just a few kilometers across. Considering only the two objects shown in each pair, rank the strength, from strongest to weakest, of the gravitational force acting on the asteroid on the left. (All extra credit questions have the same answer)
asteroid to Sun asteroid to Earth asteroid to Moon asteroid to asteroid asteroid to hydrogen atom
How much time does it take for a complete revolution of a satellite in close orbit about Earth?
90 minutes
If you were inside the rocket that falls toward the event horizon, you would notice your own clock to be running __________.
at a constant, normal rate as you approach the event horizon
Where is the center of gravity of the broom that Dr. Hewitt holds up?
at the balance point
Smallest particle of an element that has all the element's chemical properties. Consists of protons and neutrons in a nucleus surrounded by electrons.
atom
Standard unit of atomic mass. It is based on the mass of the common carbon atom, which is arbitrarily given the value of exactly 12. An amu of one is one-twelfth the mass of this common carbon atom.
atomic mass unit (amu)
The core of an atom, consisting of two basic subatomic particles - protons and neutrons (2 words)
atomic nucleus
Concentration of mass resulting from gravitational collapse, near which gravity is so intense that not even light can escape
black hole
The Earth's gravitational field extends:
both inside and outside the Earth and throughout the entire Universe.
The shape of a hanging flexible chain or cable when supported at its ends and acted upon by a uniform gravitational force. The intrinsic equation of the shape of the catenary is given by the hyperbolic function y = a Cosh(x/a).
catenary
Point at the center of an object's WEIGHT distribution, where the force of gravity can be considered to act.
center of gravity
Toss a wrench into the air and it will wobble about its:
center of mass
CENTER-directed force that causes an object to follow a curved or circular path
centripetal force
A coin and a ring roll down an incline starting at the same time. The one to reach the bottom first will be the:
coin
Chemical substance made of atoms of two or more different elements combined in a fixed proportion
compound
(a) In mechanics, the reaction force of squeezing material and reducing its volume. (b) In sound, the region of increased pressure in a longitudinal wave.
compression
When no external torque acts on an object or a system of objects,NO CHANGE OF ANGULAR MOMENTUM takes place. Hence, the angular momentum before an event involving only internal torques is equal to the angular momentum after the event.
conservation of angular momentum
Principle that energy cannot be created or destroyed. It may be transformed from one form into another, but the total amount of energy never changes.
conservation of energy
solid in which the constituent atoms or molecules are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions
crystal
In a machine, the ratio of useful energy output to total energy input, or the percentage of the work input that is converted to work output
efficiency
Property of a solid wherein a change in shape is experienced when a deforming force acts on it, with a return to its original shape when the deforming force is removed
elasticity
Substance composed of atoms that all have the same atomic number and, therefore, the same chemical properties
element
Anything that can change the condition of matter. Commonly defined circularly as the ability to do work; actually only describable by examples.
energy
What is the kinetic energy of a 2-kg toy car that is moving at 3 m/s?
9J (1/2 mv^2)
An Earth satellite is simply a projectile..
freely falling around the Earth
Punch Taut is a down-on-his-luck heavyweight boxer. One day, he steps on the bathroom scale and "weighs in" at 236 lb. Unhappy with his recent bouts, Punch decides to go to a different planet where he would weigh in at 118 lb so that he can compete with the bantamweights who are not allowed to exceed 118 lb. His plan is to travel to Xobing, a newly discovered star with a planetary system. Here is a table listing the planets in that system:
g(5.6/(1.7^2))
Pronunciation for the symbol: (a) (lower-case non-italic) g, Abbreviation for gram. (b) (lower-case italic) g, the symbol for the acceleration due to gravity (at the Earth's surface, 9.8 m/s2). (c) (upper-case italic) G, the symbol for the universal gravitation constant (6.67 × 10-11 N⋅m2/kg2).
gee
What is meant by the term nucleon?
A proton or neutron
Distinguish between tension and compression.
A pulled-apart object is in tension; a pushed-together one is in compression.
Suppose you are in an elevator. As the elevator starts upward, its speed will increase. During this time when the elevator is moving upward with increasing speed, your weight will be __________.
greater than your normal weight at rest
What is meant by the elastic limit for a particular object?
A spring is elastic UP TO THE LIMIT and inelastic above it.
The energy that flows from one object to another by virtue of a difference in temperature. Measured in calories or joules.
heat
Assume that all the shaded regions have exactly the same area. Rank the segments of the comet's orbit from left to right based on the length of time it takes the comet to move from Point 1 to Point 2, from longest to shortest. If you think that two (or more) of the diagrams should be ranked as equal, drag one on top of the other(s) to show this equality.
All together
An upright broom is easier to balance when the heavier end is:
highest, farther from hand
When a twirling ice skater brings her arms inward, her rotational speed:
increases
Why are all tides greatest at the time of a full Moon or new Moon?
At full Moon and new Moon, the tides from the Moon and the Sun ADD because they are IN LINE with Earth.
Why can't atoms be seen with a powerful optical microscope?
Atoms are much smaller than a wavelength of light.
Law relating the intensity of an effect to the inverse square of the distance from the cause. Gravity, electric, magnetic, light, sound, and radiation phenomena follow this law.
inverse-square law
The main reason ocean tides exist is that the pull of the Moon:
is GREATER on oceans CLOSER to the Moon Less on oceans Farther from the Moon
Atoms whose nuclei have the same number of protons but different numbers of neutrons
isotopes
Which requires more work: lifting a 50-kg sack a vertical distance of 2 m or lifting a 25-kg sack a vertical distance of 4 m?
Both take the same 1000 J. (Work = FD = mg X distance = 10mD)
For any pair of particles (or spherical objects), each particle attracts the other particle with a force that is directly proportional to the product of the masses of the particles, and inversely proportional to the square of the distance between their centers of mass.
law of universal gravitation
What are the five most common elements in humans?
C, H, O, N, and Ca
If a satellite's RADIAL velocity is zero at all times, its orbit must be
Circular
Suppose you are in an elevator that is moving upward. As the elevator nears the floor at which you will get off, its speed slows down. During this time when the elevator is moving upward with decreasing speed, your weight will be __________.
less than your normal weight at rest
Simple machine made of a bar that turns about a fixed point called the fulcrum
lever
Device for increasing (or decreasing) a force or simply changing the direction of a force
machine
After Punch Taut travels to Pentune, what actually happens to his mass and his weight?
mass remains the same; weight decreases
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 remains the same; weight decreases
ENERGY due to the POSITION or the MOVEMENT of something; potential or kinetic energy
mechanical energy
Two or more atoms of the same or different elements bonded to form a larger particle.
molecule
If an object has kinetic energy, then it also must have:
momentum
The curved PATH followed by a PROJECTILE (near the Earth's surface) under the influence of gravity only.
parabola
at an angle of 90° to a given line, plane, or surface.
perpendicular
Energy of position, usually related to the relative position of two things, such as a stone and the Earth (gravitational PE), or an electron and a nucleus (electric PE
potential energy (PE)
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
Rate at which work is done or energy is transformed, equal to the work done or energy transformed divided by time; measured in watts
power
Force per surface area where the force is normal (perpendicular) to the surface; measured in Pascals
pressure
Increasing the size makes the range of the trajectory...
Decrease
What happens to the volume of a loaf of bread that is squeezed? The mass? The density?
Decreases, stays the same, increases
Mass of a substance per unit volume.
Density
What kind of attraction pulls electrons close to the atomic nucleus?
Electric
Exactly what is it that enables an object to do work?
Energy
When is your weight measured as mg?
For a non-accelerating mass near the surface of Earth
How would you test the notion that a steel ball is elastic?
For one thing, drop both a steel ball on a steel anvil. It will bounce!
Suppose you are at the center of a large freely-rotating horizontal turntable in a carnival funhouse. As you crawl toward the edge, the angular momentum of you and the turntable:
remain the same, RPMS Decrease
What is the evidence that dark matter exists?
Gravitational forces within galaxies are too great to be accounted for with ordinary matter.
A projectile is fired vertically from the surface of the Earth at 10 km/s. The projectile will
rise/fall
Reluctance or apparent resistance of an object to change its state of rotation, determined by the distribution of the mass of the object and the location of the axis of rotation or revolution
rotational inertia
Number of rotations or revolutions per unit of time; often measured in rotations or revolutions per second or minute
rotational speed
An arch with a semicircular shape
round arch
What element has the lightest atoms?
Hydrogen
An apple hanging from a limb has potential energy because of its height. If it falls, what becomes of this energy just before it hits the ground? When it hits the ground?
Immediately before hitting the ground the apple's energy is kinetic energy; When it hits the ground, its energy becomes thermal energy.
Projectile or smaller celestial body that orbits a larger celestial body.
satellite
Study of how size affects the relationship among weight, strength, and surface area.
scaling
What did Robert Brown see under the microscope?
specks of dust moving around
If you drop a stone into a hole drilled all the way to the other side of the Earth (neglect the molten core), the stone will:
speed up until it gets to the CENTER of the Earth.
High or low tide that occurs when the SUN/EARTH/MOON are all lined up so that the tides due to the sun and moon coincide, making the high tides higher than average and the low tides lower than average
spring tides
The summation of the areas of the exposed sides of an object.
surface area
Component of velocity tangent to the trajectory of a projectile
tangential velocity
Consider Earth and the Moon. As you should now realize, the gravitational force that Earth exerts on the Moon is equal and opposite to that which the Moon exerts on Earth. Therefore, according to Newton's second law of motion __________.
the Moon has a larger acceleration than Earth, because it has a smaller mass
Where in the atom is most of its mass concentrated? What is this mass composed of?
In the nucleus as protons and neutrons
Is it easier to balance a long rod with a mass attached to it when the mass is closer to your hand or when the mass is farther away?
It is easier when the mass is farther from your hand.
Why is centrifugal force in a rotating frame called a "fictitious force"?
It is not a fundamental force of NATURE. Instead, it is a force that only appears in an accelerating frame of REFERENCE.
Predict how the horizontal component of the velocity will change with time after the projectile is fired.
It stays constant.
A car is raised a certain distance in a service-station lift, thus giving it potential energy relative to the floor. If it were raised twice as high, how much more potential energy would it have?
It would have twice as much potential energy.
Each planet moves in an elliptical orbit with the sun at one focus.
Kepler's First Law
The line from the sun to any planet sweeps out equal areas of space in equal time intervals
Kepler's Second Law
Distinguish between mass number and atomic mass.
Mass number: Number of Nucleons Atomic Mass: Total mass
Moon exerts on the spaceship (place in order)
Moon--->Earth
If the string that holds a whirling can in its circular path breaks, what kind of force causes it to move in a straight- line path: centripetal, centrifugal, or no force? What law of physics supports your answer?
No force; Newton's first law
Can we correctly say that hydrogen is a new source of energy? Why or why not?
No. It takes energy to make hydrogen.
How are most of the elements with nuclei heavier than those of hydrogen and helium formed?
Nuclear fusion in stars
The RADIAL VELOCITY of an Earth satellite is its velocity
PERPENDICULAR Radial=Perpendicular Tangential= Parallel
Any object that moves through the air or through space, acted on only by gravity (and air resistance, if any)
Projectile
Wheel that acts as a lever used to change the direction of a force.
Pulley
If you double the speed of a moving object, then the kinetic energy:
Quadruples
What is recycled energy?
Reused energy that otherwise would be wasted
If you are standing on a scale in an elevator, what exactly does the scale measure?
the force you exert on the scale
Centrifugal forces are an apparent reality to observers in a reference frame that is:
Revolving
Why does the rotational inertia of the rod with the attached mass closer to your hand compare the way it does with the rotational inertial of the rod with the attached mass farther away?
Rotational inertia depends on whether the mass is farther or closer to the point of rotation. The farther the mass is, the higher the rotational inertia.
ROTATIONAL *Speed* together with a direction for the axis of rotation or revolution.
Rotational velocity
Which will have the greater acceleration rolling down an incline: a hoop or a solid disk? Why?
Solid disk Mass closer to Axis
If you hang at rest by your hands from a long vertical rope, where is your center of gravity with respect to the rope?
Somewhere straight below where your hands grab the rope
Why were so many vertical columns needed to support the roofs of stone buildings in ancient Egypt and Greece?
Stone breaks under tension.
Product of force and lever-arm distance, which tends to produce rotational acceleration.
torque
When you put a pipe over the end of a wrench when trying to turn a stubborn nut on a bolt, this can make the wrench handle twice as long, and will change the torque by what factor?
twice as much
