Question 1

Which of the following best describes the physical quantity 'momentum'?

Accepted Answer

Momentum is a vector quantity that depends on both the mass and velocity of an object.

Question 2

A 2-kg object moves with a velocity of $$10\ \mathrm{m/s} at$$ $$37^\circ$$ above the horizontal. What is the magnitude of its momentum?

Accepted Answer

$$20\ \mathrm{kg\cdot m/s}$$

Question 3

Which equation correctly relates impulse $$J to $$the change in momentum $$\Delta p$$?

Accepted Answer

$$J = F_{\mathrm{avg}} \Delta t = \Delta p$$

Question 4

A $$0.15\ \mathrm{kg}$$ baseball is thrown at $$30\ \mathrm{m/s}$$ and is caught, coming to rest in $$0.2\ \mathrm{s}. $$What is the magnitude of the average force exerted on the ball by the glove?

Accepted Answer

$$45\ \mathrm{N}$$

Question 5

A $$1200\ \mathrm{kg}$$ car moving at $$20\ \mathrm{m/s}$$ hits a wall and comes to rest after compressing $$1.0\ \mathrm{m}$$ into the wall. What is the magnitude of the average force exerted by the wall on the car during the collision?

Accepted Answer

$$240,000\ \mathrm{N}$$

Question 6

Which of the following statements about the conservation of momentum is correct?

Accepted Answer

Momentum is conserved only when the net external force on the system is zero.

Question 7

Two ice skaters, one with mass $$50\ \mathrm{kg}$$ and the other $$70\ \mathrm{kg}$$, push off from each other on frictionless ice. If the $$50\ \mathrm{kg}$$ skater moves at $$3\ \mathrm{m/s}$$, what is the velocity of the $$70\ \mathrm{kg}$$ skater?

Accepted Answer

$$-2.14\ \mathrm{m/s}$$

Question 8

A $$10\ \mathrm{g}$$ bullet is fired into a $$5\ \mathrm{kg}$$ stationary block of wood. The bullet embeds in the block, and together they move at $$0.6\ \mathrm{m/s}$$ after the collision. What was the initial speed of the bullet?

Accepted Answer

$$300\ \mathrm{m/s}$$

Question 9

Which of the following best describes a completely inelastic collision?

Accepted Answer

Momentum is conserved, but kinetic energy is not.

Question 10

A $$0.5\ \mathrm{kg}$$ ball moving at $$10\ \mathrm{m/s} is $$caught and brought to rest. What is the impulse delivered to the ball during the catch?

Accepted Answer

$$5\ \mathrm{kg\cdot m/s}$$

Question 11

A $$70\ \mathrm{kg}$$ football player glides across very smooth ice at $$2\ \mathrm{m/s}. He $$throws a $$0.45\ \mathrm{kg}$$ football straight forward at $$15\ \mathrm{m/s}$$ relative to the player. What is the player's velocity after the throw?

Accepted Answer

$$1.90\ \mathrm{m/s}$$

Question 12

Which of the following is true for an elastic collision between two objects?

Accepted Answer

Both momentum and kinetic energy are conserved.

Question 13

A $$1.0\ \mathrm{kg}$$ block moving at $$2.0\ \mathrm{m/s}$$ collides elastically with a stationary $$1.0\ \mathrm{kg}$$ block. What are their velocities after the collision?

Accepted Answer

The first block stops, and the second block moves at $$2.0\ \mathrm{m/s}$$

Question 14

A $$0.2\ \mathrm{kg}$$ bullet is fired horizontally into a $$10\ \mathrm{kg}$$ wooden block at rest on a horizontal surface. The coefficient of kinetic friction between block and surface is $$0.4. $$The bullet embeds in the block, which then slides $$35\ \mathrm{m}$$ before stopping. What was the initial speed of the bullet?

Accepted Answer

$$525\ \mathrm{m/s}$$

Question 15

A $$5.0\ \mathrm{g}$$ bullet is shot through a $$1.00\ \mathrm{kg}$$ wood block suspended on a string $$2.00\ \mathrm{m}$$ long. The center of mass of the block rises a distance of $$11\ \mathrm{cm}. If $$the final speed of the block is $$0.45\ \mathrm{m/s}$$, what is the speed of the bullet as it emerges from the block?

Accepted Answer

$$95\ \mathrm{m/s}$$

Question 16

Which of the following is the correct formula for the center of mass $$x_{cm} of $$two masses $$m_1$$ and $$m_2$$ located at $$x_1$$ and $$x_2$$?

Accepted Answer

$$x_{cm} = \frac{m_1$ x_1$ + m_2$ x_2$}{m_1$ + m_2$}$$

Question 17

A $$70\ \mathrm{kg}$$ skater runs parallel to a $$3\ \mathrm{kg}$$ skateboard, both moving to the right at $$10\ \mathrm{m/s}. $$The skater jumps on the board. What is the final speed of the system?

Accepted Answer

$$10\ \mathrm{m/s}$$

Question 18

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

Accepted Answer

Kinetic energy is conserved.

Question 19

A $$1000\ \mathrm{kg}$$ car traveling east at $$20\ \mathrm{m/s}$$ collides with a $$3000\ \mathrm{kg}$$ truck heading north at $$10\ \mathrm{m/s}. If $$the vehicles lock together after the collision, what is the magnitude of their final velocity?

Accepted Answer

$$11.2\ \mathrm{m/s}$$

Momentum: Concepts, Applications, and Problem Solving

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