Q: A 1.0-kg ball has a velocity of 12 m/s downward just before it strikes the ground and bounces up with a velocity of 12 m/s upward. What is the change in momentum of the ball?

$$24 \, \mathrm{kg \cdot m/s}$$, \text{upward}$

Question 1

A 1.0-kg ball has a velocity of 12 m/s downward just before it strikes the ground and bounces up with a velocity of 12 m/s upward. What is the change in momentum of the ball?

Accepted Answer

$$24 \, \mathrm{kg \cdot m/s}$$, 	ext{upward}$

Question 2

Which of the following best describes the impulse delivered to an object?

Accepted Answer

The product of the average force and the time interval during which the force acts: $$J = F_{	ext{avg}} \Delta t$$

Question 3

A tennis ball falls and bounces off the ground. Which statement is true concerning the momentum of the ball and the Earth during the collision?

Accepted Answer

The momentum of the ball and the momentum of the Earth both change.

Question 4

A 54-kg woman and an 88-kg man push off against each other on frictionless ice. If the woman moves away with a speed of $$2.5 \, \mathrm{m/s}$$, what is the recoil velocity of the man?

Accepted Answer

$$-1.5 \, \mathrm{m/s}$$

Question 5

Which of the following is true for an elastic collision in one dimension?

Accepted Answer

Both total momentum and total kinetic energy are conserved.

Question 6

Two train cars, each of mass $$m$$, are moving toward each other with equal speeds $$v$$ and collide head-on, sticking together. What is their final velocity after the collision?

Accepted Answer

$$0$$

Question 7

A $$0.15 \, \mathrm{kg}$$ baseball is hit by a bat, changing its velocity from $$-40 \, \mathrm{m/s} to$$ $$+50 \, \mathrm{m/s} in$$ $$0.002 \, \mathrm{s}. $$What is the average force exerted by the bat on the ball?

Accepted Answer

$$6750 \, \mathrm{N}$$

Question 8

Which equation correctly expresses the conservation of momentum for a two-object system in a one-dimensional collision?

Accepted Answer

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

Question 9

In a completely inelastic collision, two objects stick together after colliding. Which of the following is true?

Accepted Answer

Momentum is conserved, but kinetic energy is not.

Question 10

A $$0.2 \, \mathrm{kg}$$ ball moving at $$5 \, \mathrm{m/s}$$ collides elastically with a $$0.3 \, \mathrm{kg}$$ ball at rest. What is the velocity of the $$0.2 \, \mathrm{kg}$$ ball after the collision?

Accepted Answer

$$-1 \, \mathrm{m/s}$$

Question 11

A ballistic pendulum is used to measure the speed of a bullet. The bullet of mass $$m$$ embeds itself in a block of mass $$M$$ suspended from a string. If the combined mass rises to a height $$h$$, what was the initial speed $$v_0 of $$the bullet?

Accepted Answer

$$v_0$$ = \frac{(M+m)}{m} \sqrt{2gh}$$

Question 12

Which of the following best describes an internal force in a system?

Accepted Answer

A force that objects within the system exert on each other

Question 13

A curling stone of mass $$m_1$$ slides on ice with velocity $$v_{1i}$$ and collides with a stationary stone of mass $$m_2. $$After the collision, $$m_1$$ moves at $$v_{1f} at an $$angle $$	heta$$ and $$m_2$$ moves at $$v_{2f}. $$Which law allows you to solve for the final velocities?

Accepted Answer

Conservation of linear momentum in both $$x$$ and $$y$$ directions

Question 14

A $$2.0 \, \mathrm{kg}$$ cart moving at $$3.0 \, \mathrm{m/s}$$ collides and sticks to a $$1.0 \, \mathrm{kg}$$ cart at rest. What is their final velocity?

Accepted Answer

$$2.0 \, \mathrm{m/s}$$

Question 15

Which of the following is a correct statement about the direction of impulse?

Accepted Answer

Impulse has the same direction as the average force applied.

Question 16

A $$0.5 \, \mathrm{kg}$$ ball moving at $$4 \, \mathrm{m/s}$$ collides elastically with a $$0.5 \, \mathrm{kg}$$ ball at rest. What are their velocities after the collision?

Accepted Answer

First ball: $$0 \, \mathrm{m/s}$$, second ball: $$4 \, \mathrm{m/s}$$

Question 17

A firework explodes into two pieces of masses $$m_1$$ and $$m_2$$ that fly apart with velocities $$v_1$$ and $$v_2. If $$the firework was initially at rest, what is the relationship between the velocities?

Accepted Answer

$$m_1$$ $$v_1$$ = -$$m_2$$ $$v_2$$

Question 18

Which of the following is NOT a way to change the momentum of an object?

Accepted Answer

Keeping the object's velocity and mass constant

Impulse, Momentum, and Collisions: Study Notes

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