Question 1

A tennis ball strikes a racket and rebounds. Which statement best describes the impulse delivered to the ball during the collision?

Accepted Answer

Impulse is the area under the force-versus-time graph during the collision.

Question 2

A 0.5 kg ball moving at 2 m/s collides elastically with a stationary 0.5 kg ball. What are the final velocities of both balls after the collision?

Accepted Answer

The first ball stops, and the second ball moves at 2 m/s.

Question 3

Which equation correctly expresses the momentum principle for a single object?

Accepted Answer

$$\Delta p_x = J_x$$

Question 4

A rocket burns fuel and ejects exhaust gases downward. Which statement about momentum is correct?

Accepted Answer

The momentum of the rocket and exhaust gases together is conserved if no external forces act.

Question 5

In a perfectly inelastic collision, two objects stick together after impact. Which equation describes their final velocity?

Accepted Answer

$$v_f = \frac{m_1$ v_{i1} + m_2$ v_{i2}}{m_1$ + m_2$}$$

Question 6

A force acts on a ball for a short time interval, changing its velocity. Which formula gives the impulse delivered to the ball?

Accepted Answer

$$J_x = \int_{t_i}^{t_f} F_x(t) dt$$

Question 7

A 10 g projectile traveling east at 2 m/s explodes into three fragments. One fragment moves west at 10 m/s, another moves 40° north of east at 12 m/s. What principle should be used to find the speed and direction of the third fragment?

Accepted Answer

Conservation of momentum in two dimensions

Question 8

Which statement about the conservation of momentum in a system of particles is correct?

Accepted Answer

The total momentum changes only if external forces act on the system.

Question 9

During a collision, the force exerted on an object varies with time. How can the impulse be calculated if the force-time graph is complicated?

Accepted Answer

By integrating the force over time: $$J_x = \int_{t_i}^{t_f} F_x(t) dt$$

Question 10

A ball is dropped from a height above the Earth. When is momentum conserved?

Accepted Answer

Momentum is conserved only if the system includes both the ball and the Earth.

Question 11

Which equation expresses Newton’s second law in terms of momentum?

Accepted Answer

$$\vec{F} = \frac{d\vec{p}}{dt}$$

Question 12

In a perfectly elastic collision where $$m_1$$ \gg $$m_2$$, what are the approximate final velocities of the two balls?

Accepted Answer

$$v_{f1} \approx v_{i1}$$, $$v_{f2} \approx 2 v_{i1}$$

Question 13

Which of the following is NOT a characteristic of a perfectly inelastic collision?

Accepted Answer

Mechanical energy is conserved.

Question 14

A system of three particles interacts only through internal forces. What determines the change in total momentum?

Accepted Answer

The sum of external forces acting on the system.

Question 15

Which formula gives the final velocity of Ball 1 after a perfectly elastic collision with Ball 2 initially at rest?

Accepted Answer

$$v_{f1} = \frac{m_1$ - m_2$}{m_1$ + m_2$} v_{i1}$$

Question 16

Which real-world scenario is best modeled as a perfectly inelastic collision?

Accepted Answer

A dart hitting and sticking to a dartboard.

Question 17

Which statement about impulse is correct?

Accepted Answer

Impulse is the area under a force-versus-time graph for a single component.

Question 18

A collision occurs in a system with no external forces. What happens to the total momentum?

Accepted Answer

The total momentum remains constant.

Question 19

Which equation describes the conservation of momentum in two dimensions?

Accepted Answer

$$\sum p_{x,i} = \sum p_{x,f}$$ and $$\sum p_{y,i} = \sum p_{y,f}$$

Impulse, Momentum, and Collisions: Principles and Applications

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