AnswersPOP Physics 2627Impulse and Momentum

Conservation of Momentum Answers

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A train car has a mass of 10,000 kg and is moving at +3.0 m/s. It strikes an identical train car that is at rest. The train cars combine.

A
0 m/s
B
1.5 m/s
C
3.0 m/s
D
6.0 m/s
2
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A 35-gram stainless steel ball on a track is moving at a velocity of 9 m/s. On the same track, a 75-gram stainless steel ball is moving at a velocity of –7 m/s. After colliding, the 35-gram ball moves at a velocity of –15 m/s. Assume there is no net force on the system.What is the velocity of the 75-gram ball after the collision? Round to the nearest tenth.

A
–4.2 m/s
B
–0.5 m/s
C
0.5 m/s
D
4.2 m/s
4

In a game of pool, a 0.4 kg cue ball is traveling at +0.80 m/s when it hits a slower striped ball moving at +0.38 m/s. After the collision, the striped ball moves off at +0.62 m/s.

A
0.20 m/s
B
0.56 m/s
C
1.0 m/s
D
1.8 m/s
5

Two grocery carts have the same initial total momentum. The two carts collide, and now cart B has a greater final velocity.

A
It is less if cart B has a smaller mass.
B
It is greater if cart B has a greater mass.
C
It is the same if no external forces are added.
D
It depends on the masses of cart A and cart B.
6

Two blocks are initially at rest with a compressed spring between them. When the spring is released, the 2m block moves to the left and the m block moves to the right. This represents an inelastic collision in a closed system.

Question illustration
A
The total energy is zero.
B
The total momentum is zero.
C
The momentum of the m block is zero.
D
The momentum of the 2m block is zero.
7

A ball has a mass of 0.25 kg and is moving to the right at 1.0 m/s. It hits a ball of mass 0.15 kg that is initially at rest. After the collision, the 0.15 kg ball moves off to the right with a velocity of 0.75 m/s.

A
0.42 m/s to the right
B
0.42 m/s to the left
C
0.55 m/s to the right
D
0.55 m/s to the left
8

Momentum data about the same objects in the same closed system is shown below.

Question illustration
A
3.4
B
3.5
C
3.6
D
3.7
9

In a lab, two identical lab carts (m = 1.0 kg) travel toward each other, each with a speed of 2 m/s. The cars collide, and one cart moves to the right with a speed of 3 m/s and the other moves left with a speed of 2 m/s.

A
This experiment did not occur in a closed system.
B
This proves the conservation of momentum since pi = pf .
C
An additional mass was added to one cart, which explains the increase in speed.
D
The increase in speed was due to the kinetic energy from one cart transferring to the other.
10

For a movie stunt, an empty truck with a mass of 2000 kg goes 10 m/s and runs into a stopped car of mass 1000 kg. The truck then keeps moving and pushes the car along with it.

A
The collision is perfectly elastic.
B
Kinetic energy stays the same.
C
The momentum after the collision is greater than the momentum before the collision.
D
The speed of the combined vehicles is less than the initial speed of the truck.
11

Which are examples of perfectly inelastic collisions? Check all that apply.

A
a baseball bouncing off a bat
B
bumper cars bumping off of each other
C
a cue ball hitting an eight ball and stopping
D
a plane landing on an aircraft carrier
E
rain sticking to a window
F
two train cars coupling together
12

Which equation best describes the law of conservation of momentum?

A
pi = pf
B
pi > pf
C
pi < pf
D
pi + pf = 0
13

A girl is standing still in the middle of a baseball field. The girl catches the baseball and begins to move in the same direction as the thrown ball.

A
inelastic, since the girl moves in the same direction as the thrown ball
B
inelastic, since the girl moves in the opposite direction of the thrown ball
C
elastic, since the girl moves in the same direction as the thrown ball
D
elastic, since the girl moves in the opposite direction of the thrown ball
14

A basketball player passes a ball to a teammate at a velocity of 6 m/s. The ball has a mass of 0.51 kg. If the original player has a mass of 59 kg and there is no net force on the system, what is the velocity of the player after releasing the ball? Let a positive velocity be in the direction of the pass.

A
–0.05 m/s
B
–0.5 m/s
C
–0.6 m/s
D
–6 m/s
15

Two identical carts travel at the same speed toward each other, and then a collision occurs. The graphs show the momentum of each cart as a function of time, both before and after the collision.Which graph shows a perfectly inelastic collision?

A
There is a graph with time in seconds on the x axis and the y axis is labeled P in kilogram meters per second. There is a red horizontal line that drops down below the x axis and is the farther away from the x axis and a horizontal line. A blue line is the mirror image starting below the x axis and ending above the x axis. The red line is labeled car A and a blue line labeled car B. At the point both graphs cross the x axis is labeled collision.
Option A
B
A graph with momentum on the y axis measured in kilogram meters per second and time on the x axis measured in seconds. There are no values on the axes. There are two curves on the graph. The first starts above the x axis and is horizontal before curving downward to the x axis labeled 2 m cart. The second curve starts below the axis, the same distance below as the first one was above, and is horizontal before curving upward toward the x axis at the same time and labeled m cart. Where they meet is labeled Collision. Both curves meet at the x axis at the same time and are both on the x axis for a time period labeled Combined carts.
Option B
C
A graph with momentum on the y axis measured in kilogram meters per second and time on the x axis measured in seconds. There are no values on the axes. There are two curves on the graph the first starts above the x axis and is horizontal before curving downward toward the x axis labeled 2 m cart. The second curve starts below the axis, a smaller distance below as the first one was above, and is horizontal before curving upward toward and crosses the x axis and is labeled m cart. Where they meet is labeled Collision. Both curves meet above the axis at the same time and both go horizontal above the x axis for a time period labeled Combined carts.
Option C
D
There is a graph with time in seconds on the x axis and the y axis is labeled P in kilogram meters per second. There is a red horizontal line that drops down below the x axis and is then farther away from the x axis and a horizontal line. A blue line is the mirror image starting below the x axis and ending above the x axis. The red line is labeled car A and a blue line labeled car B. At the point both graphs cross the x axis is labeled collision.
Option D
16

[BLANK]

A
force
B
impulse
C
momentum
D
velocity

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