Q: A force of 10 N acts on a 2 kg object for 5 seconds. What is the impulse delivered to the object?

$$I = 50\ \text{N}\cdot\text{s}$$

Q: What is the gravitational force between two 5 kg masses separated by 2 meters? ($$G = 6.67 \times 10$$^{-11}$$\ \text{N}\cdot\text{m}^2/\text{kg}^2)$$

$$F = 8.34 \times 10$$^{-11}$$\ \text{N}$$

Question 1

A 2 kg ball moving at 3 m/s collides head-on with a stationary 1 kg ball. If the collision is perfectly elastic, what is the velocity of the 1 kg ball after the collision?

Accepted Answer

$$v = 3\ 	ext{m/s}$$

Question 2

Which of the following best describes impulse?

Accepted Answer

Impulse is a vector quantity equal to the change in momentum.

Question 3

A car of mass 1000 kg moving at 20 m/s collides with a stationary truck of mass 3000 kg. If the collision is completely inelastic, what is the final velocity of the combined mass?

Accepted Answer

$$v = 5\ 	ext{m/s}$$

Question 4

Which scenario best illustrates the conservation of momentum?

Accepted Answer

Two ice skaters pushing off from each other and moving in opposite directions.

Question 5

A force of 10 N acts on a 2 kg object for 5 seconds. What is the impulse delivered to the object?

Accepted Answer

$$I = 50\ 	ext{N}\cdot	ext{s}$$

Question 6

Which of the following statements about work is correct?

Accepted Answer

Work is zero if the force is perpendicular to the displacement.

Question 7

A 5 kg object is lifted vertically by 2 meters. What is the work done against gravity?

Accepted Answer

$$W = 98\ 	ext{J}$$

Question 8

A spring with a spring constant $$k = 200\ 	ext{N/m} is $$compressed by $$0.1\ 	ext{m}. $$What is the elastic potential energy stored?

Accepted Answer

$$E = 1\ 	ext{J}$$

Question 9

At what point in a pendulum's swing is its kinetic energy the highest?

Accepted Answer

At the lowest point of the swing.

Question 10

A roller coaster car starts from rest at the top of a hill of height $$h. $$Ignoring friction, what is its speed at the bottom?

Accepted Answer

$$v = \sqrt{2gh}$$

Question 11

Which of the following is the correct formula for angular velocity?

Accepted Answer

$$\omega = \frac{	heta}{t}$$

Question 12

A 2 kg mass is attached to a string and swung in a circle of radius 1 m at a speed of 4 m/s. What is the centripetal force?

Accepted Answer

$$F_c = 32\ 	ext{N}$$

Question 13

Which of the following best describes torque?

Accepted Answer

Torque is a vector quantity equal to force times lever arm.

Question 14

A figure skater spins faster when she pulls her arms in. Which principle explains this?

Accepted Answer

Conservation of angular momentum

Question 15

What is the gravitational force between two 5 kg masses separated by 2 meters? ($$G = 6.67 	imes 10$$^{-11}$$\ 	ext{N}\cdot	ext{m}^2/	ext{kg}^2)$$

Accepted Answer

$$F = 8.34 	imes 10$$^{-11}$$\ 	ext{N}$$

Question 16

Which of the following best explains why astronauts experience weightlessness in orbit?

Accepted Answer

They are in free fall around Earth.

Question 17

Which of the following is NOT a cause of ocean tides?

Accepted Answer

The temperature of ocean water

Question 18

A projectile is launched horizontally from a cliff. Which statement is true about its horizontal velocity?

Accepted Answer

Horizontal velocity remains constant.

Question 19

What is the escape velocity from Earth? (Earth's mass $$M = 5.97 	imes 10$$^{24}$$\ 	ext{kg}$$, radius $$R = 6.37 	imes 10^6$\ 	ext{m}$$, $$G = 6.67 	imes 10$$^{-11}$$\ 	ext{N}\cdot	ext{m}^2/	ext{kg}^2)$$

Accepted Answer

$$v_{esc} = 11.2\ 	ext{km/s}$$

Question 20

Which of the following best describes the difference between mass density and weight density?

Accepted Answer

Mass density is mass per unit volume; weight density is weight per unit volume.

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