1.A truck and a bicycle travel along the same road at the same speed. Which one carries the greater momentum?

1. The bicycle, because it is easier to speed up
2. They carry equal momenta, because their speeds are equal
3. The truck, because momentum grows with mass
4. Neither, until the direction of travel is given

2.The impulse delivered to an object is equal to

1. the change in its momentum
2. the change in its kinetic energy
3. its momentum after the force stops acting
4. the net force acting on it

3.Two carts collide on a level, frictionless track. Taking the two carts together as the system, the total momentum of the system after the collision is

1. larger than before, because the carts pushed on each other
2. equal to what it was before the collision
3. smaller than before, because kinetic energy was lost
4. zero, because the two pushes are equal and opposite

4.Two gliders on a level track carry momenta that are equal in magnitude and opposite in direction. Which statement about the system is correct?

1. The total momentum and the total kinetic energy are both zero
2. The total momentum is zero only if the two masses are equal
3. The total kinetic energy is zero and the total momentum is not
4. The total momentum is zero and the kinetic energy is not

5.A firecracker at rest on a frictionless table bursts into three pieces. Immediately after the burst, the total momentum of the three pieces is

1. zero, because the pieces move in all directions
2. not zero, because the pieces are now moving
3. zero, because nothing pushed the system from outside
4. not zero, because the burst released energy

6.A gymnast bends her knees as she lands. Compared with a landing that keeps the legs straight, bending the knees

1. lengthens the stopping time, so the average force is smaller
2. lowers the impulse the floor delivers to her
3. lowers her change in momentum
4. raises the average force on her but shortens the stopping time

7.A graph of the momentum of a cart against time is a horizontal line that sits above the time axis. Which statement about the cart is correct?

1. It is at rest
2. No net force acts on it
3. A constant net force acts on it
4. Its momentum is rising at a steady rate

8.A single cart rolls along a rough, level track and slows down. Taking the cart alone as the system, its momentum is not constant. The best reason is that

1. momentum is conserved only in elastic collisions
2. momentum is never constant for a system of one object
3. the cart is losing mass to the track
4. friction from the track is an external force on this system

9.Two carts collide on a level track and stick together. Compared with before the collision, the total momentum and the total kinetic energy of the system are

1. both unchanged
2. both smaller
3. the momentum unchanged and the kinetic energy smaller
4. the momentum smaller and the kinetic energy unchanged

10.A problem states that two gliders collide elastically. What information does the word elastically supply?

1. The total kinetic energy afterward equals the total before
2. The total momentum of the system is conserved
3. The gliders move off together after the collision
4. Each glider keeps the kinetic energy it arrived with

11.A student says that because momentum is conserved when an object at rest bursts into two pieces, the two pieces must move apart at equal speeds. The best correction is that

1. momentum is conserved only when the two pieces have equal masses
2. the momenta match in size, so the lighter piece is faster
3. the speeds are equal only when the burst is elastic
4. momentum is not conserved when an object bursts apart

12.A ball is dropped and bounces back up from the floor at a smaller speed than it arrived with. Taking up as positive, the impulse the floor delivers to the ball is

1. negative, because the ball has slowed down
2. zero, because the ball reverses direction
3. positive, and smaller in size than the ball’s arriving momentum
4. positive, and larger in size than the ball’s arriving momentum

13.A puck slides north and strikes a second puck that is at rest. After the collision the first puck moves northwest. Which statement about the second puck must be true?

1. Its eastward momentum matches the first puck’s westward momentum
2. It moves due north
3. It moves northwest as well, along a parallel line
4. Its momentum is equal in size to the momentum of the first puck

14.Two carts collide on a level track. Afterward the total kinetic energy of the system is one third of what it was before. The collision was

1. elastic
2. perfectly inelastic
3. inelastic, though not necessarily perfectly inelastic
4. impossible, because kinetic energy cannot fall in a collision

15.Two carts collide on a level track and the problem says nothing about the kinetic energy. Which statement is correct?

1. Neither conservation law can be used on a collision like this
2. Momentum is conserved, and one more fact is needed
3. The total kinetic energy is conserved
4. The carts must move off together

16.A $0.40$ kg ball moves east at $5.0$ m/s. What is the magnitude of its momentum?

1. $2.0$ kg$\cdot$m/s
2. $0.080$ kg$\cdot$m/s
3. $5.0$ kg$\cdot$m/s
4. $10$ kg$\cdot$m/s

17.A constant net force of $8.0$ N acts on a cart for $0.50$ s. What is the magnitude of the impulse delivered to the cart?

1. $0.50$ N$\cdot$s
2. $8.5$ N$\cdot$s
3. $16$ N$\cdot$s
4. $4.0$ N$\cdot$s

18.A $2.0$ kg cart moving at $3.0$ m/s collides elastically with a stationary cart of the same mass. What is the total kinetic energy of the system afterward?

1. $4.5$ J
2. $6.0$ J
3. $9.0$ J
4. $18$ J

19.Cart A has mass $3.0$ kg and moves right at $2.0$ m/s. Cart B has mass $1.0$ kg and moves left at $4.0$ m/s. Taking right as positive, the momentum of the system is

1. $+10$ kg$\cdot$m/s
2. $+2.0$ kg$\cdot$m/s
3. $-2.0$ kg$\cdot$m/s
4. zero

20.The mass of a cart is doubled while its speed is cut in half. Its momentum and its kinetic energy change by factors of

1. $1$ and $\tfrac12$
2. $1$ and $1$
3. $2$ and $\tfrac12$
4. $\tfrac12$ and $\tfrac14$

21.A $0.50$ kg ball moving at $6.0$ m/s strikes a wall and rebounds along the same line at $4.0$ m/s. What is the magnitude of the change in its momentum?

1. $1.0$ kg$\cdot$m/s
2. $2.0$ kg$\cdot$m/s
3. $3.0$ kg$\cdot$m/s
4. $5.0$ kg$\cdot$m/s

22.The net force on a cart is constant at $6.0$ N for $2.0$ s, then falls in a straight line to zero over the next $2.0$ s. What total impulse is delivered to the cart?

1. $6.0$ N$\cdot$s
2. $12$ N$\cdot$s
3. $18$ N$\cdot$s
4. $24$ N$\cdot$s

23.A $4.0$ kg cart moving right at $3.0$ m/s collides with a $2.0$ kg cart at rest, and the two move off together. What is their common speed?

1. $1.0$ m/s
2. $2.0$ m/s
3. $3.0$ m/s
4. $4.5$ m/s

24.A $2.0$ kg cart moving right at $4.0$ m/s strikes a $4.0$ kg cart moving left at $1.0$ m/s. Afterward the $2.0$ kg cart moves left at $2.0$ m/s. What is the velocity of the $4.0$ kg cart?

1. $2.0$ m/s to the right
2. $0.50$ m/s to the right
3. $2.0$ m/s to the left
4. $3.0$ m/s to the right

25.During a collision, cart A pushes on cart B with an average force of $20$ N for $0.10$ s. Taking both carts as the system, these pushes change the total momentum of the system by

1. $2.0$ kg$\cdot$m/s
2. $4.0$ kg$\cdot$m/s
3. $20$ kg$\cdot$m/s
4. zero

26.A $1.0$ kg cart moving at $4.0$ m/s strikes a stationary $3.0$ kg cart and the two stick together. How much kinetic energy does the system lose?

1. $2.0$ J
2. $4.0$ J
3. $6.0$ J
4. $8.0$ J

27.Two objects carry momenta of equal magnitude. Object X has twice the mass of object Y. Which statement about their kinetic energies is correct?

1. Object Y has twice the kinetic energy of object X
2. Object X has twice the kinetic energy of object Y
3. The two kinetic energies are equal
4. Object Y has four times the kinetic energy of object X

28.A $1200$ kg truck traveling at $15$ m/s is brought to rest in $3.0$ s. What is the magnitude of the average net force on the truck?

1. $400$ N
2. $6000$ N
3. $18000$ N
4. $5400$ N

29.An object at rest on a frictionless surface bursts into three pieces. One piece carries $6.0$ kg$\cdot$m/s east and a second carries $6.0$ kg$\cdot$m/s north. What does the third piece carry?

1. $12$ kg$\cdot$m/s, directed southwest
2. $8.5$ kg$\cdot$m/s, directed northeast
3. $8.5$ kg$\cdot$m/s, directed southwest
4. zero, because the object started at rest

30.Two carts of equal mass approach each other on a level track, each moving at $3.0$ m/s, and they stick together on contact. The total kinetic energy of the system afterward is

1. one quarter of what it was before
2. one half of what it was before
3. the same as it was before
4. zero

1.A loaded shopping cart and an empty one roll at the same speed. Say which has the greater momentum and why.

2.State the two quantities that are multiplied together to give an impulse, and give the unit of impulse in two equivalent ways.

3.State the condition that has to hold before you may say the total momentum of a chosen system is constant.

4.State what is true of the total kinetic energy of the system in an elastic collision, and what is true of it in an inelastic collision.

5.Two carts each carry a momentum of magnitude $6$ kg$\cdot$m/s and they move toward each other. A student reports the total momentum of the pair as $12$ kg$\cdot$m/s. Correct the student.

6.A ball thrown at a wall bounces straight back at the speed it arrived with. Explain why the wall delivers twice the impulse it would deliver if the ball stopped dead instead.

7.Explain how a front end built to crumple protects the people in a car, even though the change in momentum of the car is the same either way.

8.Explain how a graph of force against time gives the impulse, and say what a part of the graph lying below the time axis means.

9.Two students describe the same collision between two carts. One says momentum is conserved and the other says it is not, and neither has made an arithmetic mistake. Explain how both can be correct.

10.A person standing at rest on frictionless ice throws a ball forward. Explain why the person moves backward, using momentum rather than forces.

11.Explain why the forces the two carts in a collision exert on each other cannot change the total momentum of the pair.

12.A ball falls toward the ground. Explain why its momentum is not constant when the ball alone is taken as the system, and why the total is constant when the ball and the Earth are taken as the system.

13.A collision between two carts leaves the system with less kinetic energy than it started with. A student says energy was destroyed. Correct the student and say where the energy went.

14.Explain why the word elastic in a problem statement is a piece of information you can use, and state what it gives you.

15.Explain how a system of two moving objects can have a total momentum of zero while carrying a large total kinetic energy, and explain why a system with zero total kinetic energy cannot have a nonzero total momentum.

16.Explain why Newton’s second law is not a separate law standing beside the impulse momentum theorem, and state the condition under which one becomes the other.

17.A push on a cart at rest is made to last three times as long while the impulse is held fixed. Describe what happens to the average force and to the final speed of the cart, and justify both using the area under the force against time graph.

18.Describe how you would choose the system when you want to avoid dealing with a particular force, and explain why making that choice is allowed.

19.A puck sliding east strikes a second puck at rest and leaves the collision moving north of east. Without calculating anything, explain why the second puck must carry momentum toward the south, and say what happens to that southward momentum if the first puck instead leaves at a steeper angle at the same speed.

20.Two carts start with the same two masses and the same two velocities. Explain why the outcome in which they stick together removes the most kinetic energy, and why no outcome can remove more.