Q: Which of the following best defines impulse in physics?

Impulse is the product of force and time interval: $$I = F \times \Delta t$$

Q: A 3.6-kg chihuahua charges at a speed of 3.3 m/s. What is its momentum?

$$p = m \times v = 3.6 \times 3.3 = 11.88\ \mathrm{kg\cdot m/s}$$

Q: If a force of 10 N is applied to a 2-kg object for 0.5 seconds, what is the impulse delivered to the object?

$$I = F \times \Delta t = 10 \times 0.5 = 5\ \mathrm{N\cdot s}$$

Q: A 1700-kg rhino charges at a speed of 50 km/h. What is the magnitude of the average force needed to bring the rhino to a stop in 0.50 s?

$$F = \frac{\Delta p}{\Delta t} = \frac{1700 \times (\frac{50}{3.6})}{0.5} = 47,222\ \mathrm{N}$$

Question 1

A slowly moving ship can have a greater momentum than a fast-moving car because:

Accepted Answer

The ship's mass is much greater than that of the car.

Question 2

Which of the following best defines impulse in physics?

Accepted Answer

Impulse is the product of force and time interval: $$I = F 	imes \Delta t$$

Question 3

A 3.6-kg chihuahua charges at a speed of 3.3 m/s. What is its momentum?

Accepted Answer

$$p = m 	imes v = 3.6 	imes 3.3 = 11.88\ \mathrm{kg\cdot m/s}$$

Question 4

If a force of 10 N is applied to a 2-kg object for 0.5 seconds, what is the impulse delivered to the object?

Accepted Answer

$$I = F 	imes \Delta t = 10 	imes 0.5 = 5\ \mathrm{N\cdot s}$$

Question 5

Which of the following statements about momentum is correct?

Accepted Answer

Momentum is a vector quantity and is calculated as the product of an object's mass and velocity: $$p = m 	imes v$$

Question 6

A 1700-kg rhino charges at a speed of 50 km/h. What is the magnitude of the average force needed to bring the rhino to a stop in 0.50 s?

Accepted Answer

$$F = \frac{\Delta p}{\Delta t} = \frac{1700 	imes (\frac{50}{3.6})}{0.5} = 47,222\ \mathrm{N}$$

Question 7

Which of the following best explains why follow-through is important in sports like golf or baseball?

Accepted Answer

It increases the time over which the force is applied, resulting in a greater impulse and thus a greater change in momentum.

Question 8

In a collision between two billiard balls of equal mass, one moving and one at rest, what happens to the total momentum of the system?

Accepted Answer

The total momentum of the system is conserved.

Question 9

A cannonball is fired from a cannon. What happens to the momentum of the cannon-cannonball system?

Accepted Answer

The total momentum of the system is conserved; the forward momentum of the cannonball is balanced by the backward momentum of the cannon.

Question 10

Which equation expresses the conservation of momentum for a system of two objects before and after a collision?

Accepted Answer

$$m_1 v$$_{1i} + $$m_2 v$$_{2i} = $$m_1 v$$_{1f} + $$m_2 v$$_{2f}$$

Question 11

In an inelastic collision, which of the following is always true?

Accepted Answer

Momentum is conserved, but kinetic energy is not.

Question 12

A large concrete block is dropped onto a truck moving at a constant velocity. What happens to the magnitude of the truck's velocity?

Accepted Answer

It decreases to keep momentum constant, with $$v_{new} = \frac{m_{truck} v_{truck}}{m_{truck} + m_{block}}$$

Question 13

Suppose two identical train cars are on the same track. The first car is moving at 10 m/s toward the stationary second car. If they couple together upon contact, what will the newly connected train's speed be?

Accepted Answer

$$v_{final} = \frac{m v}{2m} = \frac{10}{2} = 5\ \mathrm{m/s}$$

Question 14

Which of the following statements about elastic collisions is correct?

Accepted Answer

In elastic collisions, both momentum and kinetic energy are conserved.

Question 15

A cue ball strikes an eight-ball head-on in a game of pool. The cue ball comes to rest after the collision. What can be said about the eight-ball?

Accepted Answer

The eight-ball moves away with the same velocity the cue ball had before the collision.

Question 16

Which of the following best describes the effect of increasing the time interval over which a force is applied to an object?

Accepted Answer

It decreases the average force required to achieve the same change in momentum.

Question 17

A 2-kg object moving at 4 m/s collides elastically with a stationary 2-kg object. What is the velocity of the first object after the collision?

Accepted Answer

$$v_{1f} = 0\ \mathrm{m/s}$$

Question 18

Which of the following is the correct expression for the change in momentum (impulse) of an object?

Accepted Answer

$$\Delta p = F \Delta t$$

Question 19

A ball is dropped from a height and bounces back up. If the ball bounces to a lower height than it was dropped from, what can be said about the collision with the ground?

Accepted Answer

The collision is inelastic; some kinetic energy is lost.

Question 20

Which of the following is a real-world example of the conservation of momentum?

Accepted Answer

A gun recoiling backward when a bullet is fired forward.

Momentum and Impulse: Principles, Applications, and Conservation

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