Download momentum review answer key

A freight car with a mass of 3. 0 x l 05 k§ travels at a velocity of 2. 5 m;,. It collides with a.
stationary car having a mass of 1.8 x 10 kg. The cars connect and roll together after the impact.
What is the velocity of the connected cars?
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A block of mass 5 kg is moving with a velocity of9 mis when it collides with an 8. kg mass
moving with a velocity of 5 m;s in the opposite direction. If the masses remain hooked together
after the collision, what will their common velocity be?
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Physics Ch 6 .Review
Mul tiple Choice
ldenti/jl the choice that best completes the statement or answers the question.
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l. The change in an object's momentum is equal to
a . the product of the mass of the object and the time i.ntervaJ.
b. the product of the force applied to the object and the time interval.
c. the time interval divided by the net external force.
d. the net external force divided by the time interval.
2. The impulse experienced by a body is equivalent to the body's change in
a . velocity.
c. momentum.
b. l.inetic energy.
d. force.
3. A large moving ball collides with a small stationary ball. The momentum
a. of the large ball decreases, and the momentum of the small ball increases.
b. of the small ball decreases, and the momentum of the large ball increases.
c. of the large ball increases, and the momentum of the small ball decreases.
d. does not change for either bal1.
4. Two skaters stand facing each other. One skater's mass is 60 kg, and the other's mass is 72 kg. If the skaters
push away from each other without spinning,
a. the 60 kg skater travels at a lower momentum.
b. their momenta are equal but opposite.
c. their total momentum doubles.
d. their total momentum decreases.
5. A swimmer with a mass of75 kg dives off a raft with a mass of 500 kg. If the s,vimmer's speed is 4 mis
immediately after leaving the raft, what is the speed of the raft?
a. 0.2 m/s
c. 0.6 m/s
b. 0.5 m/s
d. 4.0 mis
6: Two objects move separately after co11ic1tng, and both the total momentum and total kinetic energy remain
constant. Identify the type of collision.
a. elastic
.
c. inelastic
b. perfectly elastic
d. perfectly inelastic
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7. A l .5 x 10 kg truck moving at 15 mis strikes a 7 .5 x 102 kg automobile stopped at a traffic light. The vehicles
hook bumpers and skid together at 10.0 mis. What is the decrease in kinetic energy?
a. I'. I x I 05 J
c. 1. 7 x 105J
b. 1.2 x 104J
d. 6.0 x 1()4J
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8. A bilJiard ball collides with a second identical ball in elastic head-on collision. What is the kinetic energy of
the system after the coHision compared with the kinetic energy before the collision?
a. unchanged
c. two times as great
b. one-fourth as great
d. four times as great
9. An object with a mass of O. IO kg makes an elastic head-on collision with a stationary object with a mass of
0. J5 kg. The final velocity of the 0.10 kg object after the collision is - 0.045 m/s and the final velocity of the
0.15 kg object after the collision is 0.16 mis. What was the initial velocity of the 0.10 kg object?
a. 0 . .16 mis
c. 0.20 mis
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JO. During latmch, a Space.Shultle continuously increases its velocity. How does this change in velocity affect the
shuttle's momentum?
a.
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momentum increases
b. momentum decreases
c. momentum remains the same
11. As a rocket bums fuel, its mass decreases. How does the loss in mass affect a rocket's momentum?
a.
momentum increases
momentum decreases
mernentum remains the same
12. Two identical vehicles are traveling together on a highway. Vehicle A has a lower velocity than vehicle B.
Compare the momentum of vehicle A to the momentum of vehicJe B.
a. Vehicle A has a greater momentum
b. Vehicle B has a greater momentum
c. Both vehic.Jes have the same momentum
d. Their momenta cannot be compared because velocity does not affect momentum
13. Tina and Marci are in a fierce debate over whether or not a sma11 car and large truck of greater mass can
have the same momentum. Tina says that they definitely cannot l1ave the same momentum, and she asks Marci
to give one example of how the car's momentum can equal the truck's momentum. Which of the following
responses can Marci cite?
b.
c.
a
I.
The car and the truck will have the same momentum if their velocities are equal
Il. The car and the truck will have the same momentum if their velocities are both zero.
III. The car and the truck will have the same mom(?ntum if the car is moving at a higher velocity than
the truck.
IV. The car and the truck will have the same momentum if the product of the car's mass and velocity is
equal to the product of the truck's mass and velocity.
a.
b.
C.
L
C
I and II
Il and Ill
11 and JV
III and IV
14. A fireworks rocket is fired into the air, and just before exploding, it is moving straight upward at 30 mis. Just
after exploding, the rocket is separated into two equal masses. One mass is moving straight upward at 40 mis.
With what velocity is the second mass travelling?
a. Downward at 20 mis
b. Downward at 40 mis
c. Upward at 20 mis
d. Upward at 40 mis
d.
1s. An adult driving a bumper car travelling East collides head-on with a stationary bumper car with a small child
fllirul(I,
at the wheel. Assuming the collision ii
1Jastic, with what speed and direction will the adult's car be
moving after the collision?
·
a. The adult will be travelling faster than he was before the collision, travelling East
b. The adult will be travelling faster than he was before the collisio~ travelling West
c. TI1e adult will be travelling slower than he was before the collision, travelling East
d. ~he adult will be trave11ing slower than he was before the coUision, travelling \Vest
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lD : A
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C
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A
16. Roberto and his girlfriend Shianna arc skating around town on their in-line skates. At one point, Roberto is
behind Shianna and is traveling faster and cannot stop. How will their individual speeds change after Roberto
crashes into Shiruma in an inelastic collision?
a. Their speeds will both increase
b. Their speeds will both decrease
c. Roberto 's speed will increase and Sh.ianna's speed will decrease
d. Roberto's speed will decrease and Sh.ianna's speed will increase
17. Of the following choices, which shows a conservation of momentum equation constrnctccl properly for a system
of two masses coUiding inelastically?
a . 1111V1 = m1vu·+ m2v2r
, V1r* V2r
b. m1v1 + m2v2 = m1V1r+ m2V2r
, v,r* V2r
C.
ffi1V1 + ffi2V2 = (m1 + m 2)Vr
d. m1v1 + m2v2 = (m 1 + m2)(v1r + v21)
18. A grenade sits motionless on a tree stump and then explodes. Its peices, which have different masses, move
away from the tree stump in all directions and at very high velocities. The statements below compare the
grenade before the explosion to all of the moving peices just after the explosion. Select the statement that is
true.
a. The momentum of the grenade is less than the sum of the momenta of all the peices.
b. The momentum oftbe grenade is equal to the sum of the momenta of its peices.
c. AJI of the peices move away from the stump at the same speed.
d. The velocity of the grenade is less than the sum of the velocities of its peices.
19. When a baseball is hit, it undergoes a change in momentum of70 kg·m/s and is in contact with the baseball bat
for 0.10 seconds. What force has been applied to the ball?
a. 7N
b. 70N
C.
700 N
d. 7000 N
20. Some performers train themselves to enact awesome feats of strength and skill. One amazing feat is to break
through 10 vertically-stacked cement blocks with only the force of the performer's forehead. How can a
light-wei.g ht cloth laid down on the top brick protect the performer from breaking her head along with the
blocks?
a.
The cloth will increase the time the performer's head is in contact with the brick, which
slightly decreases the applied force .
TI1e cloth will increase the time the perfonner's head is in contact with the brick, which
decreases the change in momentum.
c. The cloth will decrease the time the performer's head is in contact with the brick, which
slightly decreases the applied force.
d. The cloth wi.Jl decrease the time the performer's head is in contact with the brick, which
decreases the change in momentum.
21. Dwayne and Stewart have challenged eachother to see who can send a football the farthest distance. Dwayne
will throw the football, and Stewart will kick the football. Dwayne applies a thrm:ving force of 12.5 N to the
football over a time period of0.80 seconds and Stewart applies a kicking force of 50 N over a 0.20 second time
period. Who applies a larger change in momentum to the football ?
a. Dwayne
b. Stewart
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22.
ID: A
A truck \Vith a mass of 4000 kg and a I 000 kg car are traveling together with the same velocity when their
drivers notice the traffic light ahead turn yellow. ff they both apply the same brcakiJ1g force and come to a
stop, how wilJ the stopping times of the two vehicles compare'?
a. The truck will stop in the same amount of time as the car
b. The tmck \vill take 4 times longer to stop than the car
c. The tmck will take 16 times longer to stop than the car
d. TI1e tmck wiJl take 1/4 of the time it takes the car to stop