AnswersPOP Physics 2627Conservation of Momentum

Conservation of Momentum Answers

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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.

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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.
2
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A large blue marble of mass 3.5 g is moving to the right with a velocity of 15 cm/s. The large marble hits a small red marble of mass 1.2 g that is moving to the right with a velocity of 3.5 cm/s. After the collision, the blue marble moves to the right with a velocity of 5.5 cm/s.

A
9.2 cm/s
B
14 cm/s
C
24 cm/s
D
31 cm/s
3

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.
4

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
5

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
6

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
7

An empty 2,500 kg train car is headed northbound at a velocity of 5 m/s. Ahead of the first car, an empty 1,500 kg car is headed northbound on the same track at 1 m/s. The faster train bumps into the slower one, and they combine into one train.What is the velocity of the two-car train?

A
1 m/s
B
3 m/s
C
3.5 m/s
D
5 m/s
8

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
9

A bowling ball has an initial momentum of +30 kg m/s and hits a stationary bowling pin. After the collision, the bowling ball leaves with a momentum of +13 kg • m/s.

A
0 kg • m/s
B
11 kg • m/s
C
17 kg • m/s
D
43 kg • m/s
10

forceimpulsemomentumvelocity

A
force
B
impulse
C
momentum
D
velocity
11

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.
12

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
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

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.
15

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.
16

Which equation best describes the law of conservation of momentum?

A
pi = pf
B
pi > pf
C
pi < pf
D
pi + pf = 0
17

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

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