Momentumpractice Problems

Momentumpractice Problems

MomentumPractice Problems

PSI AP Physics BName______

Multiple Choice

  1. A truck moves along a frictionless level road at a constant speed. The truck is open on top. A large load of gravel is suddenly dumped into the truck. What happens to the velocity of the truck?

(A) It increases (B) It remains the same (C) It decreases

(D) more information is required (E) it stops immediately

  1. A steel ball and a piece of clay have equal mass. They are dropped from the same height on a horizontal steel platform. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the platform. Which object experiences the greater momentum change?

(A) the ball (B) the clay (C) Both experience the same momentum change

(D) there is no momentum change for either (E) more information is required

  1. A car of mass m is moving with a momentum p. How would you represent its kinetic energy in terms of these two quantities?

(A) p2/(2m) (B) 1/2 mp2 (C)mp (D) mp/2 (E) zero

  1. When a ping-pong ball rolling with a speed of 3.0 m/s collides with a bowling ball at rest, the ping-pong's speed after the collision will be, approximately,

(A) 0 (B) 3.0 m/s (C) 6.0 m/s (D) 12 m/s (E) 9.0 m/s

  1. A bowling ball moving with speed v collides head-on with a stationary tennis ball. The collision is elastic, and there is no friction. The bowling ball barely slows down. What is the speed of the tennis ball after the collision?

(A) nearly v (B) nearly 2v (C) nearly 3v (D) nearly infinite (E) Zero

Questions 6-8

  1. Two blocks are on a frictionless surface and have the same mass m. Block 2 is initially at rest. Block 1 moves to the left with speed 4v. Block 1 collides inelastically with block 2. Which of the following choices is closest to the final speed of the system of two blocks?

(A) v (B) 2v (C) 3v(D) 4v(E) 5v

  1. Two blocks are on a frictionless surface and have the same mass m. Block 2 is initially at rest. Block 1 moves to the left with speed 4v. Block 1 collides elastically with block 2. What is the final speed of block 1?

(A) zero (B) v (C) 2v(D) 3v(E) 4v

  1. Two blocks are on a frictionless surface and have the same mass m. Block 2 is initially at rest. Block 1 moves to the left with speed 4v. Block 1 collides elastically with block 2. What is the final speed of block 2?

(A) v (B) 2v (C) 3v(D) 4v(E) 7v

  1. An object with a mass of 2 kilograms is accelerated from rest. The graph shows the magnitude of the net force as a function of time. At t=4 seconds the object’s velocity would have been closest to which of the following?

(A) 2m/s(B) 4 m/s(C) 10 m/s

(D) 13m/s(E)cannot be determined

  1. A 3 kg ball is dropped onto a concrete floor. What is the magnitude of the ball’s change in momentum if its speed just before striking the floor is 7 m/s and its rebound speed is 3 m/s?

(A) 10 kg m/s(B) 15 kg m/s(C) 30 kg m/s(D) 50 kg m/s

(E) 70 kg m/s

  1. A spring is compressed between two blocks with unequal masses, m1 and m2, held together by a string as shown in the figure to the right. The objects are initially at rest on a horizontal surface with no friction. The string is then cut. What is true of the two object system after the string is cut?

(A)The net final kinetic energy is zero

(B)The velocities of the two objects are equal in magnitude but opposite in direction

(C)The kinetic energy of each block is equal and opposite

(D)Kinetic energy remains the same as before the string was cut

(E)The net final momentum of the two objects is zero

  1. A toy truck moves freely along a track at 2 m/s and collides with a toy Subaru that is at rest. After the collision, the two cars stick together and move continuously. What is the magnitude of the velocity of both vehicles after the collision if the toy truck weighs 3 kg and the toy Subaru weighs 1 kg.

(A) 1.5 m/s(B) 2 m/s(C) 3m/s(D) 5 m/s(E) 6 m/s

Questions 13-14

  1. A hockey stick hitting a 0.5 kg puck is in contact with the ball for a time of .05 seconds. The puck travels in a straight line as it approaches and then leaves the hockey stick. If the puck arrives at the stick with a velocity of 6.4 m/s and leaves with a velocity of -3.6 m/s. What is the magnitude of the change in momentum of the puck?

(A) 2kg·m/s (B) 3kg·m/s (C) 5kg·m/s (D) 6kg·m/s (E) 10kg·m/s

  1. A hockey stick hitting a 0.5 kg puck is in contact with the ball for a time of .05 seconds. The puck travels in a straight line as it approaches and then leaves the hockey stick. If the puck arrives at the stick with a velocity of 6.4 m/s and leaves with a velocity of -3.6 m/s, what is the magnitude of the average force acting on the puck?

(A) 100 N (B) 150 N (C) 200 N (D) 300 N (E) 500N

  1. A kickball is rolled by the pitcher at a speed of 10 m/s. The kicker kicks the ball. The magnitude of the force on the kickball that the kicker’s foot exerts on the ball is always

(A)Zero because only the ball exerts a force on the foot

(B)Equal to the vertical component of gravity acting on the kickball

(C)Larger than the force the kickball exerts on the foot

(D)Smaller than the force the kickball exerts on the foot

(E)Equal to the force that the kickball exerts on the foot

Questions 16-17

  1. An object of mass 3 kg starts from rest and moves along the x-axis. A net horizontal force is applied to the object in +x direction. The force time relations presented by the graph. What is the net impulse delivered by this force?

(A)6 N·s (B) 8 N·s (C)24 N·s

(D) 30 N·s (E) 36 N·s

  1. An object of mass 3 kg starts from rest and moves along the x-axis. A net horizontal force is applied to the object in +x direction. The force time relations presented by the graph. What is the net work done on the object?

(A)30 J (B) 50 J (C) 90 J (D) 150 J (E) 120 J

  1. A constructor is initially at rest on an icy pond throws a hammer. After being thrown the hammer moves in one direction while the constructor moves off in the other direction. Which of the following correctly describes this occurrence?

(A) The constructor and the hammer will have equal amounts of kinetic energy

(B)The hammer will have the greater magnitude of momentum

(C)The constructor will have the greater magnitude of momentum

(D)The hammer will have greater kinetic energy

(E)They both will have equal and opposite amounts of momentum

  1. A 40 kg physics student at rest on a frictionless rink throws a 3 kg box, giving the box a velocity of 8 m/s. Which statement describes the motion of the physics student afterwards most accurately?

(A)0.9 m/s in the same direction as the box

(B)0.6 m/s in the opposite direction of the box

(C)0.8 m/s in the same direction as the box

(D)3.4 m/s in the same direction as the box

(E)1.6 m/s in the opposite direction of the box

  1. A rubber ball with a mass of 0.25 kg and a speed of 9 m/s collides perpendicularly with a wall and bounces off with a speed of 11 m/s in the opposite direction. What is the magnitude of the impulse acting on the rubber ball?

(A)1 kg m/s(B)2 kg m/s(C) 5 kg m/s(D)20 kg m/s(E)25 kg m/s

  1. A 10,000-kg trolley moving at 4 m/s collides and couples with a 6000-kg trolley which is initially at rest. The nearest final speed of these two trolleys is:

(A)0.5 m/s(B) 1 m/s(C) 2 m/s(D)2.5 m/s(E) 3 m/s

  1. When the velocity of a moving object is quadrupled, which of the following is also quadrupled?

(A)kinetic energy(B) acceleration(C) momentum

(D) potential energy(E) all of the above

  1. Two friends with mass 60 kg and 40 kg run directly toward each other with speeds 3 m/s and 2 m/s respectively. If they hug each other as they collide, the combined speed of the two friends just after the collision will be

(A)0m/s(B) 1 m/s(C) 1.6 m/s(D) 2 m/s(E) 3 m/s

  1. How long must a 60 N net force act to produce a change in momentum of 240 kg m/s?

(A)1 s(B)2 s(C)3 s(D) 4 s(E) 5 s

  1. A tennis ball of mass m rebounds from a vertical wall with the same speed v as it had initially. What is the change in momentum of the ball?

(A)mv (B) 2mv (C) 2mvcosθ

(D) 2mvsinθ (E) zero

  1. Which of the following is true about an object of mass m1 moving on a horizontal frictionless surface strikes and sticks to an object of mass m2 (m1>m2)?

(A)The kinetic energy is conserved during the collision

(B)The momentum is conserved during the collision

(C)The momentum is zero after the collision

(D)The object m1 has greater momentum after the collision than before the collision

(E)The object m2 has greater momentum after the collision then before the collision

  1. A steel ball moving at a constant speed v on a horizontal frictionless surface collides obliquely with an identical ball initially at rest. The velocity of the first ball before and after the collision is presented on the diagram. What is the approximate direction of the velocity of the second ball after the collision?

(A) (B) (C)

(D) (E)

Questions 28-29

  1. A stationary cannon ball explodes in three pieces of masses m, m, and 2m. The two momenta of equal masses presented by the diagram. What is the direction of the momentum of 2m mass?

(A) (B) (C)

(D) (E)

  1. What is the magnitude of the velocity of 2m cannon ball piece?

(A)/2 V (B) /2 V (C) /2 V (D) ½ V (E) 3/2 V

  1. An object with an initial momentum shown on the diagram collides with another object at rest. Which of the following combinations of two vectors may represent the momenta of the two objects after the collision?

(A) (B) (C)

(D) (E)

Questions 31 – 32

A 6 kg block moves with a constant speed 5 m/s on a horizontal frictionless surface and collides elastically with an identical block initially at rest. The second block collides and sticks to the last 6 kg block initially at rest.

  1. What is the speed of the second 6 kg block after the first collision?

(A)zero (B) 2 m/s (C) 2.5 m/s (D) 3 m/s (C) 5 m/s

  1. What is the speed of the third 6 kg block after the second collision?

(A)zero (B) 2 m/s (C) 2.5 m/s (D) 3 m/s (C) 5 m/s

Questions 33 – 34

Object A with mass 8 kg travels to the east at 10 m/s and object B with mass 3 kg travels south at 20 m/s. The two objects collide and stick together.

33. What is the magnitude of the velocity they have after the collision?

(A) 1.8 m/s (B) 9.1 m/s(C) 12.7 m/s

(D) 20 m/s(E) 25.5 m/s

34. What is the direction of the velocity they have after the collision?

(A) 30º south of east(B) 37º south of east

(C) 45º south of east(D) 53º south of east

(E) 60º south of east

Free Response Problems

  1. Block 1 with a mass of 500 g moves at a constant speed of 5 m/s on a horizontal frictionless track and collides and sticks to a stationary block 2 mass of 1.5 kg. Block 2 is attached to an unstretched spring with a spring constant 200 N/m.
  1. Determine the momentum of block 1 before the collision.
  2. Determine the kinetic energy of block 1 before the collision.
  3. Determine the momentum of the system of two blocks after the collision.
  4. Determine the velocity of the system of two blocks after the collision.
  5. Determine the kinetic energy of the system two blocks after the collision.
  6. Determine the maximum compression in the spring after the collision.
  1. A 20 g piece of clay moves with a constant speed of 15 m/s. The piece of clay collides and sticks to a massive ball of mass 900 g suspended at the end of a string.
  1. Calculate the momentum of the piece of clay before the collision.
  2. Calculate the kinetic energy of the piece of clay before the collision.
  3. What is the momentum of two objects after the collision?
  4. Calculate the velocity of the combination of two objects after the collision.
  5. Calculate the kinetic energy of the combination of two objects after the collision.
  6. Calculate the change in kinetic energy during the collision.
  7. Calculate the maximum vertical height of the combination of two objects after the collision.
  1. A 10 g bullet moves at a constant speed of 500 m/s and collides with a 1.5 kg wooden block initially at rest. The surface of the table is frictionless and 70 cm above the floor level. After the collision the bullet becomes embedded into the block. The bullet-block system slides off the top of the table and strikes the floor.
  1. Find the momentum of the bullet before the collision.
  2. Find the kinetic energy of the bullet before the collision.
  3. Find the velocity of the bullet-block system after the collision.
  4. Find the kinetic energy of the bullet-block after the collision.
  5. Find the change in kinetic energy during the collision.
  6. How much time it takes the bullet-block system to reach the floor?
  7. Find the maximum horizontal distance between the table and the striking point on the floor.
  1. Block A with a mass of m is released from the top of the curved track of radius r. Block A slides down the track without friction and collides inelastically with an identical block B initially at rest. After the collision the two blocks move distance X to the right on the rough horizontal part of the track with a coefficient of kinetic friction µ.
  1. What is the speed of block A just before it hits block B?
  2. What is the speed of the system of two blocks after the collision?
  3. What is the kinetic energy of the system of two blocks after the collision?
  4. How much energy is lost due to the collision?
  5. What is the stopping distance X of the system of two blocks?

  1. Two discs of masses m1 = 2kg and m2 = 8 kg are placed on a horizontal frictionless surface. Disc m1 moves at a constant speed of 8 m/s in +x direction and disc m2 is initially at rest. The collision of two discs is perfectly elastic and the directions of two velocities presented by the diagram.
  1. What is the x- component of the initial momentum of disc m1?
  2. What is the y- component of the initial momentum of disc m1?
  3. What is the x- component of the initial momentum of disc m2?
  4. What is the y- component of the initial momentum of disc m2?
  5. What is the x- component of the final momentum of disc m1?
  6. What is the x-component of the final momentum of disc m2?
  7. What is the y-component of the final momentum of disc m2?
  8. What is the final vector velocity of m2?
  9. What is the y-component of the final momentum of disc m1?
  10. What is the final vector velocity of disc m1?

Multiple Choice

  1. C
  2. A
  3. A
  4. B
  5. B
  6. B
  7. A
  8. D
  9. A
  10. C
  11. E
  12. A
  13. C
  14. A
  15. E
  16. D
  17. D
  18. E
  19. B
  20. C
  21. D
  22. C
  23. B
  24. D
  25. C
  26. B
  27. C
  28. B
  29. A
  30. E
  31. E
  32. C
  33. B
  34. B

Free Response

1.

a. 2.5 kg m/s

b. 6.25 J

c. 2.5 kg m/s

d. 1.25 m/s

e. 1.56 J

f. 0.12 m

2.

a. 0.3 kg m/s

b. 2.25 J

c. 0.3 kg m/s

d. 0.33 m/s

e. 0.05 J

f. -2.2 J

g. 0.006 m

3.

a. 5 kg m/s

b. 1250 J

c. 3.3 m/s

d. 8.2 J

e. -1241 J

f. 0.38 s

g. 1.25 m

4.

a. (2gr)1/2

b. (2gr)1/2/2

c. grm/2

d. –mgr/2 (half is lost)

e. r/4μ

5.

a. 16 kg m/s

b. 0

c. 0

d. 0

e. 0

f. 16 kg m/s

g. 9.2 kg m/s

h. 2.3 m/s

i. -9.2 kg m/s

j. 4.6 m/s

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