Question 1

A soccer player kicks a stationary ball, and the force applied by the foot rises quickly to a maximum and then falls back to zero. Which of the following best describes the impulse delivered to the ball?

Accepted Answer

The impulse is the area under the force-versus-time curve during contact.

Question 2

A 0.25 kg ball moving at $$1.3\ \mathrm{m/s} to $$the right strikes a wall and rebounds to the left at $$1.1\ \mathrm{m/s}. $$What is the change in the ball’s momentum?

Accepted Answer

$$0.60\ \mathrm{kg\cdot m/s} to $$the left

Question 3

Which of the following statements about impulse is correct?

Accepted Answer

Impulse is a vector quantity and points in the direction of the average force.

Question 4

A force acts on a 10 kg cart for 2 seconds, changing its velocity from $$2\ \mathrm{m/s} to$$ $$-1\ \mathrm{m/s}. $$What is the magnitude of the impulse delivered to the cart?

Accepted Answer

$$30\ \mathrm{kg\cdot m/s}$$

Question 5

The impulse-momentum theorem can be written as:

Accepted Answer

$$\vec{J} = \Delta \vec{p} = m\vec{v}_f - m\vec{v}_i$$

Question 6

A 150 g baseball is thrown at $$20\ \mathrm{m/s}$$ and hit straight back at $$40\ \mathrm{m/s}. If $$the contact time is $$0.60\ \mathrm{ms}$$, what is the average force exerted by the bat on the ball?

Accepted Answer

$$15,000\ \mathrm{N}$$

Question 7

Which of the following best explains why airbags in cars reduce injuries during collisions?

Accepted Answer

They increase the duration of the collision, reducing the average force.

Question 8

A light plastic cart and a heavy steel cart are both pushed with the same force for $$1.0\ \mathrm{s}$$, starting from rest. After the force is removed, the momentum of the light plastic cart is:

Accepted Answer

Equal to that of the heavy steel cart

Question 9

Which of the following is a correct statement of the law of conservation of momentum for an isolated system?

Accepted Answer

The total momentum before an interaction equals the total momentum after the interaction.

Question 10

A hedgehog falls from a tree and rolls into a ball, increasing the time it takes to come to rest. According to the impulse-momentum theorem, what is the effect on the force experienced by the hedgehog?

Accepted Answer

The force decreases because the time increases.

Question 11

Which of the following is true about the momentum of a system subject only to internal forces?

Accepted Answer

The total momentum of the system is conserved.

Question 12

A force-time graph for a collision is a triangle with a base of $$8.0\ \mathrm{ms}$$ and a height of $$300\ \mathrm{N}. $$What is the impulse delivered during the collision?

Accepted Answer

$$1.2\ \mathrm{N\cdot s}$$

Question 13

Which of the following is the preferred unit for impulse in physics?

Accepted Answer

$$\mathrm{kg\cdot m/s}$$

Question 14

If the net external force on a system is zero, what can be said about the system?

Accepted Answer

The system's total momentum is conserved.

Question 15

A baseball bat delivers an impulse of $$9.0\ \mathrm{kg\cdot m/s} to a$$ $$0.15\ \mathrm{kg}$$ baseball in $$0.60\ \mathrm{ms}. $$What is the maximum force exerted if the force-time curve is triangular?

Accepted Answer

$$30,000\ \mathrm{N}$$

Question 16

Which of the following best describes the impulse approximation?

Accepted Answer

It ignores small forces during the brief time of the impulsive force.

Question 17

A system consists of two objects colliding. According to Newton’s third law, what can be said about the impulses they exert on each other?

Accepted Answer

The impulses are equal in magnitude and opposite in direction.

Question 18

Which of the following is NOT a step in drawing a before-and-after visual overview for a momentum problem?

Accepted Answer

List the positions and times of the objects.

Chapter 9: Momentum – Impulse, Momentum, and Conservation

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