1 Exam With Correct Solutions.
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. The velocity of the truck:
a. Increases
b. remains the same
c. decreases
d immediately goes to zero - Answer C. Decreases
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. p^2/2m
b. 1/2p^2m
c. pm
d. pm/2 - Answer a. p^2/2m
When a ping pong ball rolling with a speed of 3m/s collides with a bowling ball at rest, the ping
pong's speed after the collision will be close to
a. 0 m/s
b. 3 m/s
c. 6 m/s
d. 12 m/s - Answer b. 3 m/s
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 4v - Answer b. nearly 2v
, b. v
c. 2v
d. 4v - Answer c. 2v
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 and collides elastically with block 2. What is the final
speed of block 1?
a. zero
b. v
c. 2v
d. 4v - Answer a. zero
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 and collides elastically with block 2. What is the final
speed of block 2?
a. zero
b. v
c. 2v
d. 4v - Answer d. 4v
a spring is compressed between two blocks with unequal masses, m1 and m2, held together by
a spring as shown above. The objects are initially at rest on a horizontal surface with no friction
a. the velocities of the two objects are equal in magnitude but opposite in direction
b. the kinetic energy of each block is equal in magnitude but opposite in direction
c. the kinetic energy remains the same as before the string was cut
d. the net final momentum of the two objects is zero - Answer d. the net final momentum of
the two objects is zero
a carpenter is initially at rest on an icy pond when he decides to throw his hammer. After being
thrown, the hammer moves in one direction while the carpenter moves off in the opposite
direction. Which of the following correctly describes this activity?
a. the carpenter and the hammer will have the same kinetic energy
b. the hammer will have a greater magnitude of momentum