AnswersPOP Physics 2627Conservation of Momentum

Conservation of Momentum Answers

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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
4

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.

i
inelastic, since the girl moves in the same direction as the thrown ball
i
inelastic, since the girl moves in the opposite direction of the thrown ball
e
elastic, since the girl moves in the same direction as the thrown ball
e
elastic, since the girl moves in the opposite direction of the thrown ball
6

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.

T
The collision is perfectly elastic.
K
Kinetic energy stays the same.
T
The momentum after the collision is greater than the momentum before the collision.
T
The speed of the combined vehicles is less than the initial speed of the truck.
8

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.

T
This experiment did not occur in a closed system.
T
This proves the conservation of momentum since pi = pf .
A
An additional mass was added to one cart, which explains the increase in speed.
T
The increase in speed was due to the kinetic energy from one cart transferring to the other.
9

A rubber bullet of mass m is fired from a rifle into a stationary block of 25 m. The bullet remains in the block and both the bullet and the block move off with a common velocity. Assume this is an inelastic collision in a closed system.

A
The final momentum of the bullet/block is zero.
B
The final momentum of the bullet/block is equal to the initial momentum of the bullet.
C
The final momentum of the bullet/block is less than the initial momentum of the bullet.
D
The final momentum of the bullet/block is more than the initial momentum of the bullet.
10

Two carts, one of mass 2m and one of mass m, approach each other with the same speed, v. When the carts collide, they hook together. Assume that positive momentum is to the right.Which graph best represents the momentum of both carts over time, before and after the collision?

Question illustration
A
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 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
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 D
11

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.
12

[BLANK]

A
force
B
impulse
C
momentum
D
velocity
13

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
14

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.

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