Sections
Chapter Review

# Chapter Review

### Concept Items

#### 8.1Linear Momentum, Force, and Impulse

1.

What is impulse?

1. Change in velocity
2. Change in momentum
3. Rate of change of velocity
4. Rate of change of momentum
2.

In which equation of Newton’s second law is mass assumed to be constant?

1. $F=maF=ma$
2. $F=ΔpΔtF=ΔpΔt$
3. $F=ΔpΔtF=ΔpΔt$
4. $F=ΔmΔaF=ΔmΔa$
3.
What is the SI unit of momentum?
1. $N$
2. $kg⋅m$
3. $kg⋅m/s$
4. $kg⋅m/s2$
4.

What is the equation for linear momentum?

1. $p=mvp=mv$
2. $p=m/vp=m/v$
3. $p=mv2p=mv2$
4. $p=12mv2p=12mv2$

#### 8.2Conservation of Momentum

5.

What is angular momentum?

1. The sum of moment of inertia and angular velocity
2. The ratio of moment of inertia to angular velocity
3. The product of moment of inertia and angular velocity
4. Half the product of moment of inertia and square of angular velocity
6.

What is an isolated system?

1. A system in which the net internal force is zero
2. A system in which the net external force is zero
3. A system in which the net internal force is a nonzero constant
4. A system in which the net external force is a nonzero constant

#### 8.3Elastic and Inelastic Collisions

7.

In the equation p1 + p2 = p'1 + p'2 for the collision of two objects, what is the assumption made regarding the friction acting on the objects?

1. Friction is zero.
2. Friction is nearly zero.
3. Friction acts constantly.
4. Friction before and after the impact remains the same.
8.

What is an inelastic collision?

1. when objects stick together after impact, and their internal energy is not conserved
2. when objects stick together after impact, and their internal energy is conserved
3. when objects stick together after impact, and always come to rest instantaneously after collision
4. when objects stick together after impact, and their internal energy increases

### Critical Thinking Items

#### 8.1Linear Momentum, Force, and Impulse

9.
Consider two objects of the same mass. If a force of $100N$ acts on the first for a duration of $1s$ and on the other for a duration of $2s$, which of the following statements is true?
1. The first object will acquire more momentum.
2. The second object will acquire more momentum.
3. Both objects will acquire the same momentum.
4. Neither object will experience a change in momentum.
10.

Cars these days have parts that can crumple or collapse in the event of an accident. How does this help protect the passengers?

1. It reduces injury to the passengers by increasing the time of impact.
2. It reduces injury to the passengers by decreasing the time of impact.
3. It reduces injury to the passengers by increasing the change in momentum.
4. It reduces injury to the passengers by decreasing the change in momentum.
11.

How much force would be needed to cause a 17 kg ⋅ m/s change in the momentum of an object, if the force acted for 5 seconds?

1. 3.4 N
2. 12 N
3. 22 N
4. 85 N

#### 8.2Conservation of Momentum

12.

A billiards ball rolling on the table has momentum p1. It hits another stationary ball, which then starts rolling. Considering friction to be negligible, what will happen to the momentum of the first ball?

1. It will decrease.
2. It will increase.
3. It will become zero.
4. It will remain the same.
13.

A ball rolling on the floor with momentum p1 collides with a stationary ball and sets it in motion. The momentum of the first ball becomes p'1, and that of the second becomes p'2. Compare the magnitudes of p1 and p'2.

1. Momenta p1 and p'2 are the same in magnitude.
2. The sum of the magnitudes of p1 and p'2 is zero.
3. The magnitude of p1 is greater than that of p'2.
4. The magnitude of p'2 is greater than that of p1.
14.

Two cars are moving in the same direction. One car with momentum p1 collides with another, which has momentum p2. Their momenta become p'1 and p'2 respectively. Considering frictional losses, compare (p'1 + p'2 ) with (p1 + p2).

1. The value of (p'1 + p'2 ) is zero.
2. The values of (p1 + p2) and (p'1 + p'2 ) are equal.
3. The value of (p1 + p2) will be greater than (p'1 + p'2 ).
4. The value of (p'1 + p'2 ) will be greater than (p1 + p2).

#### 8.3Elastic and Inelastic Collisions

15.
Two people, who have the same mass, throw two different objects at the same velocity. If the first object is heavier than the second, compare the velocities gained by the two people as a result of recoil.
1. The first person will gain more velocity as a result of recoil.
2. The second person will gain more velocity as a result of recoil.
3. Both people will gain the same velocity as a result of recoil.
4. The velocity of both people will be zero as a result of recoil.

### Problems

#### 8.1Linear Momentum, Force, and Impulse

16.
If a force of $50N$ is applied to an object for $0.2s$, and it changes its velocity by $10m/s$, what could be the mass of the object?
1. $1kg$
2. $2kg$
3. $5kg$
4. $250kg$
17.

For how long should a force of 130 N be applied to an object of mass 50 kg to change its speed from 20 m/s to 60 m/s?

1. 0.031 s
2. 0.065 s
3. 15.4 s
4. 40 s

#### 8.3Elastic and Inelastic Collisions

18.

If a man with mass 70 kg, standing still, throws an object with mass 5 kg at 50 m/s, what will be the recoil velocity of the man, assuming he is standing on a frictionless surface?

1. −3.6 m/s
2. 0 m/s
3. 3.6 m/s
4. 50.0 m/s
19.
Find the recoil velocity of a $65kg$ ice hockey goalie who catches a $0.15kg$ hockey puck slapped at him at a velocity of $50m/s$. Assume that the goalie is at rest before catching the puck, and friction between the ice and the puck-goalie system is negligible.
1. $−0.12m/s$
2. $0m/s$
3. $0.12m/s$
4. $7.5m/s$