South Pasadena · Physics Name______Period___
7 · Momentum Practice Test
The Big Ideas:
Momentum Impulse Conservation of Momentum
True/False
____ 1. Momentum is a vector quantity.
____ 2. Two train cars of equal mass collide in- elastically. One car is at rest. The new
velocity of the two cars together will be twice as great as the velocity of the first car.
____ 3. In order to stop at port safely, an oil tanker will shut off its engines when about 1 mile from port?
____ 4. If a net force acts on a system, the system’s momentum will change.
____ 5. The airbag in a car, when deployed during an accident, decreases the impulse delivered to a passenger.
____ 6. If the mass and velocity of a moving object were both doubled, the object’s momentum would quadruple.
____ 7. Impulses are smaller when bouncing takes place?
* * * * * * * * * * * * * * * * * * * * * * * * * * *
8. What is the mass of an object if its momentum is 25 N ·s and its velocity is 5.0 m/s?
9. A 1.5 kg soccer ball is moving through the air with a velocity of 5.5 m/s. What is its momentum?
10. Which has more momentum, a large truck at rest on the freeway or a small car moving at
10 miles per hour on a street?
a) large truck
b) small car
c) both have the same momentum
11. A baseball of mass 210 grams, is moving at
25 m/s. What is the momentum of the baseball in Newton-seconds?
12. If the momentum of a 1.0 kg ball moving at 3.0 m/s East is represented by a vector that is 12 cm long, what length should a vector be if it represents another ball of mass 3.0 kg is moving at 2.0 m/s West?
13. If a space shuttle has a momentum of 4.5 x 10 8 N-s while being launched into space, what momentum would it have if its mass later decreased to one-half of the original mass and its speed increased to three times the original speed?
14. If the momentum of an object changes and its mass remains constant, then . .
a) its velocity is changing b) there is a force acting on it
c) it is accelerating (or decelerating) d) All of the above
· Impulse·
15. What are the units of impulse? ______or ______
16. Complete the equation F t = ______
Fill in the missing information
in the table below:
Impulse (N-s) Force (N) Time (s)
17. / 25.0 / 12.0 / ?18. / ? / 115 / 0.500
19. The change of momentum for an object is equal to
and caused by the ______given to the object.
20. Johnny hits a 0.050-kg golf ball, giving it a speed
of 75 m/s. What impulse does he impart?
21. A tennis ball may leave the racket of a top player
on the serve with a speed of 65.0 m/s. If the ball’s
mass is 0.0600 kg and it is in contact with the
racket for 0.0300 seconds,
a) What IMPULSE is delivered to the tennis ball?
b) what is the average force exerted on the ball? __
c) Would this force be enough to lift a 60 kg person Yes or No
22. When a cheerleader is thrown upward into the air
by the other cheerleaders and then she is caught
by the cheerleaders, which quantity or variable
are the cheerleaders trying to make larger during
the catch?
______
23. An L.A. Kings hockey player, hits a stationary
hockey puck of mass 0.12 kg, with a force that
lasts for a time of 1.0 x 10-2 seconds. This force
makes the puck shoot across the ice with a speed of
20.0 m/s, scoring a goal for the Kings.
How much force was exerted on the hockey puck?
24. Compare the impulse delivered by sad ball and
happy ball when they each have a mass of 25
grams and they are both moving towards a piece
of Styrofoam at a speed of 25 cm/s. Sad ball
comes to rest after the collision while happy ball
bounces and then travels away from the Styrofoam
at a speed of 25 cm/s.
Which ball do you think should deliver the greater
impulse on the Styrofoam? ______
Calculate the Impulse delivered by each ball:
(HINT: Convert grams into kilograms and cm/s into m/s and
draw a simple picture or diagram)
Picture:
Impulse delivered by
a) sad ball =
b) happy ball =
Increasing/Decreasing Momentum Bouncing
25. Impact, which is a unit of ______, is (the
same as or different from) impulse, which
has a unit of ______.
26. An example of increasing the momentum of an
object would be a golfer teeing off and trying to
increase the momentum of the golf ball. Another
example of increasing the momentum of an object
would be . .
______
______
27. When a golfer increases the time the golf club is in
contact with the golf ball, by following through in
the swing, the impulse she delivers to the golf ball
is . . ?
a) increased
b) decreased
c) unchanged
compared to not increasing the time of contact and
not following through the swing.
28. If the golfer above, swings the club faster, the
force she imparts to the golf ball will be
a) increased
b) decreased
c) unchanged
29. The combination of the two changes from the
previous two questions affects the overall impulse
by making it
a) greater
b) lesser
c) unchanged
30. Now lets look at what happens when you decrease
the momentum of an object like the car in "Back to
the Future" which ran into the barn into a stack of
hay. By hitting a stack of hay rather than hitting a
brick wall, the TIME was (decreased or increased)
circle correct answer
which then made the force of impact
(decrease or increase)
circle correct answer
which then affects the overall impulse delivered to
the car by making it
a) greater
b) smaller
c) unchanged
31. Most cars today have the safety feature of air
bags, which inflate automatically when the car
decelerates by a certain value, to bring the person's
momentum to zero. During an accident, when the
air bag is deployed, which of the following
variables actually change, compared to what
happens without airbags?
a) the impulse delivered to person is decreased
b) the force of impact is decreased
c) the time needed to bring person to rest is
increased
d) only a and b are both true
e) only b and c are both true
f) only a and c are true
g) a, b and c are all true
h) none of these three answers are true
32. From your reading, what is the name of the person
who altered the design of water wheels during the
California gold rush? ______
What did he do to make them more effective? He
changed the water wheel by making the paddles
______which made the water
______when it hit the paddle.
This design change caused the incoming water to
deliver a (greater? or lesser?) impulse to the paddle.
circle correct answer
Name______Period___
· Conservation of
Momentum·
33. Any gain of momentum by an object occurs only
by the ______of a corresponding amount
of momentum by another object.
34. In a system consisting of objects upon which no
external force is acting, the momentum of the
system is ______.
35. Two objects of equal mass approach each other
head-on with the same speed. The total
momentum of the system before the collision takes
place equals ______.
36. If the momentum of a cannon is considered
as a positive number, then after it fires a shell, the
momentum of the shell is considered ______.
37. A moving object containing a bomb explodes. If
the object had a total of 20 units of momentum just
before the explosion, its pieces would have a total of _____ units of momentum just after the
explosion.
38. (THIS QUESTION WON’T BE ON UNIT 6 TEST)A fireworks device is moving straight up through
the air with a certain momentum. It then explodes
into two pieces. One fragment travels straight
downward. What two statements can you make
about the other fragment?
·
·
39. (THIS QUESTION WON’T BE ON UNIT 6 TEST) If the fireworks device above had a total of 25
units of momentum just before the explosion,
then all of its pieces would have a total of _____
units of momentum just after the explosion.
40. Billiard ball A collides with billiard ball B, which
is motionless on a table. During the collision,
ball A loses 6 N-s of momentum. Which of the following is a possible condition for ball B after
the collision?
a) m = 2 kg, v = 3 m/s
b) m = 2 kg, v = 4 m/s
c) m = 2 kg, v = 5 m/s
d) m = 2 kg, v = 6 m/s
41. Sad ball is dropped to the ground and then just
plops on the ground and stays there. Is
momentum conserved in this example? Explain:
______
______
______
______
· Elastic Collisions·
M1 V1 + M2 V2 = M1 V’1 + M2 V’2Elastic Collision
42. A billiards ball (Ball A) has a mass of 0.10 kg
(100 grams) and it is moving toward another ball
(Ball B with identical mass) at a speed of 0.50
m/s, which is moving towards it at a speed of
0.50 m/s. If Ball A collides with Ball B and then
moves away with a velocity of –0.50 m/s, what
will be the velocity of Ball B?
a) 2.0 m/s c) .50 m/s
b) 1.0 m/s d) .36 m/s
43. Object A has a momentum of 60 N-s. Object B,
which has the same mass, is standing motionless.
Object A strikes object B and stops. If the mass of
object B is 6 kg, the velocity of object B after the
collision is ?
Before collision: ●A→ ●B
After collision: ●A ●B → v = ?
a) 0 m/s c) 60 m/s
b) 10 m/s d) 360 m/s
44. A 4.0-kg object traveling westward at 25 m/s hits a 15-kg object at rest. The 4.0-kg object bounces
eastward at 8.0 m/s.
a) What is the speed of the 15-kg object after
collision?
a) 8.0 m/s c) -8.0 m/s b) 8.8 m/s d) -8.8 m/s
b) What is the direction of the 15-kg object after
collision? West or East?
45. An 8.0-kg bowling ball is moving at a speed of 2.0 m/s and then bounces off a spring which compresses at the same speed that it had before bouncing.
(a) What is the momentum of recoil?
a) 6.0 N-s c) 8.8 m/s
b) −10 N-s d) 16 N-s
(b) What is its change in momentum?
a) 32 N-s c) 8.0 N-s
b) 16 N-s d) 6.0 N-s
(c) If the interaction with the spring occurs in
0.50 seconds, calculate the average force the
spring exerts on it.
a) 32 N c) 16 N
b) − 64 N d) – 6.0 N
· Inelastic Collisions
M1 V1 + M2 V2 = (M1 + M2)V'Inelastic Collision
46. A baseball of mass 0.095 kg is thrown into a
cardboard box filled with balls of newspaper. The
ball is thrown with a speed of 12 m/s. If the box
of newspaper has a mass of 0.150 kg, with what
speed will the box and baseball travel after
impact?
a) 2.0 m/s c) 4.0 m/s
b) 2.8 m/s d) 4.7 m/s
47. A 15-gram bullet is shot into a 5,085-gram
wooden block. The block is standing on a
frictionless surface. The block, with the bullet in
it, acquires a velocity of 1.0 m/s. Calculate the
velocity of the bullet before it struck the wooden
block.
a) 1.0 m/s c) 340 m/s
b) 290 m/s d) 480 m/s
48. If you are standing at rest on a skateboard and you
have a massive ball in one hand and a light ball in
the other hand, which one should you throw in
order to make you recoil with the greatest speed?
______
______
If you repeat the throwing motion with the same
object, but this time don’t let go of it, do you still
recoil? ______
______
· Explosions ·
(M1 + M2)V' = M1 V1 + M2 V249. A young boy of mass 45 kg is standing at rest on
a stationary skateboard of mass 2.5 kg. He loses
his balance and flies off the skateboard with a
velocity of – 2.8 m/s. What is the “recoil”
velocity of the skateboard?
a) 12 m/s c) 42 m/s
b) 39 m/s d) 50.4 m/s
50. A bullet of mass 0.65 kg is fired from a 4.0 kg
gun, with a speed of 5.0 x 102 m/s.
(a) What is the recoil velocity of the gun?
a) - 81 m/s c) - 41 m/s
b) - 59 m/s d) - 23 m/s
(b) What is the change in momentum of the bullet after it is fired?
a) 325 N-s c) 188 m/s
b) 290 N-s d) 55 N-s