Multiple Choice Identify the
choice that best completes the statement or answers the question.


1.

The momentum of an object is defined as the object's
a.  mass times its velocity.  b.  force times the time
interval.  c.  force times its acceleration.  d.  mass times it acceleration.  e.  velocity times the
time interval. 


2.

Which has more momentum, a large truck moving at 30 miles per hour or a small
truck moving at 30 miles per hour?
a.  Both have the same momentum.  b.  The small truck  c.  The large
truck 


3.

Compared to a sports car moving at 30 miles per hour, the same sports car moving
at miles per hour has
a.  twice as much momentum.  b.  four times as much
momentum.  c.  the same momentum. 


4.

If the momentum of an object changes and its mass remains constant,
a.  it is accelerating (or decelerating).  b.  there is a force acting on
it.  c.  its velocity is changing.  d.  all of the above  e.  none of the
above 


5.

The momentum change of an object is equal to the
a.  impulse acting on it.  b.  velocity change of the
object.  c.  force acting on it.  d.  force acting on it times its
velocity.  e.  object's mass times the force acting on it. 


6.

In order to increase the final momentum of a golf ball, we could
a.  increase the force acting on it.  b.  follow through when hitting the
ball.  c.  increase the time of contact with the ball.  d.  swing as hard as
possible.  e.  all of the above 


7.

The reason padded dashboards are used in cars is that they
a.  look nice and feel good.  b.  decrease the impulse in a
collision.  c.  increase the force of impact in a collision.  d.  decrease the
momentum of a collision.  e.  increase the time of impact in a
collision. 


8.

A table tennis ball launcher is fired. Compared to the force on the ball, the
force on the launcher is
a.  larger.  b.  the same.  c.  smaller. 


9.

A table tennis ball launcher is fired. Compared to the impulse on the ball, the
impulse on the launcher is
a.  smaller.  b.  larger.  c.  the
same. 


10.

Momentum of a system is conserved only when
a.  there are no internal forces acting on the system.  b.  the system is not
moving.  c.  there are no forces acting on the system.  d.  there is no net
external force acting on the system.  e.  the system has zero
momentum. 


11.

A collision is considered elastic if
a.  there is no lasting deformation.  b.  the objects don’t stick
together.  c.  the objects that collide don't get warmer.  d.  after the collision,
the objects have the same shape as before the collision.  e.  all of the
above 


12.

Suppose a girl is standing on a pond where there is no friction between her feet
and the ice. In order to get off the ice, she can
a.  bend over touching the ice in front of her and then bring her feet to her
hands.  b.  walk very slowly on tiptoe.  c.  get on her hands and knees and crawl off the
ice.  d.  throw something in the direction opposite to the way she wants to
go.  e.  all of the above will work 


13.

Which of the following has the largest momentum?
a.  A large truck parked in a parking lot  b.  A tightrope walker crossing Niagara
Falls  c.  The science building at your school  d.  A pickup truck traveling down the
highway  e.  A dog running down the street 


14.

A freight train rolls along a track with considerable momentum. If it were to
roll at the same speed but had twice as much mass, its momentum would be
a.  zero.  b.  unchanged.  c.  quadrupled.  d.  doubled. 


15.

A cannon recoils from launching a cannonball. The speed of the cannon's
recoil is small because the
a.  impulse on the cannon is less than the impulse on the cannonball.  b.  cannon has far more
mass than the cannonball.  c.  momentum of the cannon is
unchanged.  d.  force against the cannon is relatively small.  e.  none of the
above 


16.

Suppose a cannon is made of a strong but very light material. Suppose also that
the cannonball is more massive than the cannon itself. For such a system
a.  conservation of momentum would not hold.  b.  conservation of
energy would not hold.  c.  the cannon would travel faster than
cannonball.  d.  the force on the cannonball would be greater than the force on the
cannon.  e.  recoil problems would be lessened. 


17.

Two objects, A and B, have the same size and shape, but A is twice as heavy as
B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A
has a higher
a.  acceleration.  b.  momentum.  c.  speed.  d.  all of the above  e.  none of the
above 


18.

In order to catch a ball, a baseball player moves his or her hand backward in
the direction of the ball's motion. Doing this reduces the force of impact on the player's
hand principally because
a.  the time of impact is decreased.  b.  the time of impact is
increased.  c.  the velocity of the hand is reduced.  d.  the momentum of impact is
reduced.  e.  none of the above 


19.

A car traveling along the highway needs a certain amount of force exerted on it
to stop. More stopping force may be required when the car has
a.  less stopping distance.  b.  more momentum.  c.  more
mass.  d.  all of the above  e.  none of the
above 


20.

A cannon fires a cannonball. The speed of the cannonball will be the same as the
speed of the recoiling cannon
a.  if the mass of the cannonball equals the mass of the cannon.  b.  because momentum is
conserved.  c.  because velocity is conserved.  d.  because both velocity and momentum are
conserved.  e.  none of the above 


21.

When you jump off a step, you usually bend your knees as you reach the ground.
By doing this, the time of the impact is about 10 times more what it would be in a stifflegged
landing, and the average force on your body is reduced by
a.  less than 10 times.  b.  about 10 times.  c.  more than 10
times. 


22.

A karate expert executes a swift blow and splits a cement block with her bare
hand.
a.  The forces on both the block and the expert's hand have the same
magnitude.  b.  The times of impact on both the block and the expert's hand are the
same.  c.  The impulses on both the block and the expert's hand have the same
magnitude.  d.  all of the above  e.  none of the
above 


23.

A moving freight car runs into an identical car at rest on the track. The cars
couple together. Compared to the velocity of the first car before the collision, the velocity of the
combined cars after the collision is
a.  zero.  b.  one half as large.  c.  the
same.  d.  twice as large.  e.  More information is needed to
say. 


24.

Two gliders having the same mass and speed move toward each other on an air
track and stick together. After the collision, the velocity of the gliders is
a.  twice the original velocity.  b.  one half the original
velocity.  c.  zero.  d.  the same as the original
velocity.  e.  There is not enough information to say. 


25.

A piece of putty moving with 2 kgm/s of momentum strikes and sticks to a heavy
bowling ball that is initially at rest. After the putty sticks to the ball, both are set in motion
with a combined momentum that is
a.  less than 2 kgm/s.  b.  2 kgm/s.  c.  more than 2
kgm/s.  d.  There is not enough information to say. 


26.

The force that accelerates a rocket into outer space is exerted on the rocket by
a.  the exhaust gases.  b.  Earth's gravity.  c.  atmospheric
pressure.  d.  rocket's wings.  e.  none of the
above 


27.

Suppose an astronaut in outer space wishes to toss a ball against a very massive
and perfectly elastic concrete wall and catch it as it bounces back. If the ball is as massive as the
astronaut, then
a.  the astronaut's time between catches will decrease as the game
progresses.  b.  the astronaut will never catch the first bounce.  c.  the astronaut will
catch one bounce only.  d.  none of the
above 


28.

Superman is at rest in space when he throws an asteroid that has more mass than
he does. Which moves faster, Superman or the asteroid?
a.  Superman  b.  The asteroid  c.  They both move at
the same speed. 


29.

A cannonball shot from a longbarrel cannon travels faster than one shot from a
shortbarrel cannon because the cannonball receives a greater
a.  force.  b.  impulse.  c.  both A and
B  d.  neither A nor B 


30.

While rollerskating, Granny collides with her tiny grandson Ambrose who is at
rest. Ignoring any friction effects, Ambrose's speed after the collision will be greatest when
a.  Granny catches him and they both move together.  b.  he and Granny make a
bouncing collision, each going in opposite directions. 


31.

A 2kg ball is thrown at 3 m/s. What is the ball's momentum?
a.  2 kg·m/s  b.  3 kg·m/s  c.  6
kg·m/s  d.  9 kg·m/s  e.  none of the
above 


32.

A 4.0kg ball has a momentum of 20.0 kg·m/s. What is the ball's
speed?
a.  0.2 m/s  b.  5.0 m/s  c.  20.0
m/s  d.  80.0 m/s  e.  none of the
above 


33.

A ball is moving at 6.0 m/s and has a momentum of 24.0 kg·m/s. What is the
ball's mass?
a.  0.3 kg  b.  4.0 kg  c.  24.0
kg  d.  144.0 kg  e.  none of the
above 


34.

A 5.0kg chunk of putty moving at 10.0 m/s collides with and sticks to a 7.0kg
bowling ball that is initially at rest. The bowling ball with its putty passenger will then be set in
motion with a momentum of
a.  0 kg·m/s.  b.  2.0 kg·m/s.  c.  15.0
kg·m/s.  d.  50.0 kg·m/s.  e.  more than 50.0
kg·m/s. 

True/False Indicate whether the
statement is true or false.


35.

Momentum is defined as an object's mass times its velocity.


36.

Impulse is defined as the force exerted on an object times the time it
lasts.


37.

If the net external force acting on a system is zero, then the total momentum of
the system is zero.


38.

When two objects collide and completely bounce apart with no lasting deformation
or generation of heat, the collision is said to be elastic.


39.

When two objects collide and stick together, the collision is said to be
inelastic.


40.

Perfectly elastic collisions between large objects are uncommon in the everyday
world.


41.

When a baseball player follows through in hitting the ball, the contact time
with the ball is longer.


42.

Automobile dashboards that are padded lengthen the time of impact in case of a
collision.


43.

If a net force acts on a system, the system's momentum will change.

Essay These are not graded
online. These should be done on your practice worksheet given to you
in class. To check the answers to these click on the answers link on the
CP intro page.


44.

In terms of momentum change, explain why it is best to "give" when
catching a baseball. Provide other examples of situations in which you want to lengthen the impact
time in a collision.


45.

Why would a .22 rifle bullet travel farther than a .22 pistol bullet shot at the
same angle? (This question refers directly to one of your study guide questions. Use the
concept of Impulse in your explanation!)


46.

What does it mean to say that momentum is conserved? Give an example where
momentum is conserved in a collision.


47.

A railroad diesel engine coasting at 12 km/h runs into a stationary flatcar. The
diesel weighs 5 times as much as the flatcar. Assuming the cars couple together, how fast are they
moving after the collision?

Problem


48.

A 10kg cement block moving horizontally at 6 m/s plows into a bank of sand and
comes to a stop in 2 s. What is the average impact force on the bank?


49.

An 8kg blob of clay moving horizontally at 2 m/s hits a 3kg blob of clay at
rest. What is the speed of the two blobs stuck together immediately after the collision?


50.

A 40kg football player leaps through the air to collide with and tackle a 50kg
player heading toward him, also in the air. If the 40kg player is heading to the right at 9 m/s and
the 50kg player is heading toward the left at 2 m/s, if the larger player stops his momentum as they
hit and all the momentum is transferred to the smaller player, how fast will the smaller player be
sent backwards?


51.

A 50kg cart moving at 100 km/h collides headon with an approaching 50kg cart
moving at 10 km/h (in the opposite direction). If the two carts stick together, what will be their
speed?


52.

A 30kg girl and a 50kg boy face each other on frictionfree roller skates. The
girl pushes the boy, who moves away at a speed of 3 m/s. What is the girl's speed?


53.

A 70kg freefloating astronaut fires 0.10kg of gas at a speed of 30 m/s from
her propulsion pistol. What is the astronaut's recoil speed?
