Q: A 0.15 kg baseball is pitched at 40 m/s and is hit straight back at 60 m/s by a bat. If the contact time between the bat and the ball is 0.02 s, what is the magnitude of the average force exerted by the bat on the ball?

$$F = \frac{\Delta p}{\Delta t} = \frac{0.15 \times (60 - (-40))}{0.02} = 750 N$$

Q: A 2 kg block slides down a frictionless incline of height 5 m. What is its speed at the bottom?

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 5} = 9.9 m/s$$

Q: A 0.5 kg mass is attached to a spring with spring constant $$k = 200 N/m $$and stretched 0.1 m from equilibrium. What is the elastic potential energy stored in the spring?

$$PE = \frac{1}{2}kx^2$ = \frac{1}{2} \times 200 \times (0.1)^2$ = 1 J$$

Q: A 3 kg object moves in a circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of the centripetal force acting on it?

$$F_c = \frac{mv^2$}{r} = \frac{3 \times 16}{2} = 24 N$$

Q: A 10 kg object is dropped from a height of 8 m. What is its velocity just before hitting the ground? (Ignore air resistance.)

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 8} = 12.5 m/s$$

Q: A 5 kg mass is spun in a horizontal circle of radius 0.5 m at an angular speed of 6 rad/s. What is its angular momentum?

$$L = I\omega = (mr^2$)\omega = 5 \times (0.5)^2$ \times 6 = 7.5 kg$$·m²/s

Q: A 1.5 kg object is moving at 10 m/s. What is its kinetic energy?

$$KE = \frac{1}{2}mv^2$ = 0.5 \times 1.5 \times 100 = 75 J$$

Question 1

A 0.15 kg baseball is pitched at 40 m/s and is hit straight back at 60 m/s by a bat. If the contact time between the bat and the ball is 0.02 s, what is the magnitude of the average force exerted by the bat on the ball?

Accepted Answer

$$F = \frac{\Delta p}{\Delta t} = \frac{0.15 	imes (60 - (-40))}{0.02} = 750 N$$

Question 2

A 2 kg block slides down a frictionless incline of height 5 m. What is its speed at the bottom?

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 5} = 9.9 m/s$$

Question 3

Which of the following best describes an inelastic collision?

Accepted Answer

Momentum is conserved, but kinetic energy is not.

Question 4

A 0.5 kg mass is attached to a spring with spring constant $$k = 200 N/m $$and stretched 0.1 m from equilibrium. What is the elastic potential energy stored in the spring?

Accepted Answer

$$PE = \frac{1}{2}kx^2$ = \frac{1}{2} 	imes 200 	imes (0.1)^2$ = 1 J$$

Question 5

A 3 kg object moves in a circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of the centripetal force acting on it?

Accepted Answer

$$F_c = \frac{mv^2$}{r} = \frac{3 	imes 16}{2} = 24 N$$

Question 6

A satellite orbits Earth in a circular orbit. Which of the following statements is true about its kinetic and potential energy?

Accepted Answer

Both kinetic and potential energy remain constant.

Question 7

A 10 kg object is dropped from a height of 8 m. What is its velocity just before hitting the ground? (Ignore air resistance.)

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 8} = 12.5 m/s$$

Question 8

A 5 kg mass is spun in a horizontal circle of radius 0.5 m at an angular speed of 6 rad/s. What is its angular momentum?

Accepted Answer

$$L = I\omega = (mr^2$)\omega = 5 	imes (0.5)^2$ 	imes 6 = 7.5 kg$$·m²/s

Question 9

Which of the following best explains why astronauts in the International Space Station appear weightless?

Accepted Answer

They are in continuous free fall around Earth, experiencing apparent weightlessness.

Question 10

A 1.5 kg object is moving at 10 m/s. What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2}mv^2$ = 0.5 	imes 1.5 	imes 100 = 75 J$$

Question 11

A 1000 kg car moving at 20 m/s collides and sticks to a stationary 1500 kg truck. What is their final velocity after the collision?

Accepted Answer

$$v_f = \frac{m_1v_1 + m_2v_2}{m_1$ + m_2$} = \frac{1000 	imes 20 + 1500 	imes 0}{2500} = 8 m/s$$

Question 12

A force of 50 N is applied at an angle of 60° to the horizontal, moving an object 4 m along the floor. How much work is done by the force?

Accepted Answer

$$W = Fd\cos	heta = 50 	imes 4 	imes \cos 60^\circ = 100 J$$

Question 13

A 2 kg mass is whirled in a circle of radius 1.5 m at a speed of 3 m/s. What is the magnitude of the torque if the force is always tangential?

Accepted Answer

$$	au = rF = r 	imes m a_c = 1.5 	imes 2 	imes \frac{9}{1.5} = 18 N$$·m

Question 14

Which of the following is true about the gravitational force between two objects?

Accepted Answer

It is always attractive and proportional to the product of their masses.

Question 15

A 0.2 m³ block of material has a mass of 500 kg. What is its mass density?

Accepted Answer

$$\rho = \frac{m}{V} = \frac{500}{0.2} = 2500 kg/m$$³

Question 16

A 60 W light bulb is left on for 2 hours. How much energy does it use?

Accepted Answer

$$E = Pt = 60 	imes 2 	imes 3600 = 432,000 J$$

Question 17

Which of the following best describes a crystalline solid?

Accepted Answer

It has an ordered, repeating atomic structure.

Question 18

A 0.3 kg ball is thrown horizontally at 15 m/s from a 20 m high cliff. How far from the base of the cliff does it land? (Ignore air resistance, $$g = 9.8 m/s$$²)

Accepted Answer

$$t = \sqrt{\frac{2h}{g}} = \sqrt{\frac{40}{9.8}} = 2.02 s$$;\ x = vt = 15 	imes 2.02 = 30.3$ m

Question 19

During a spring tide, what is the relative position of the Sun, Moon, and Earth?

Accepted Answer

They are aligned in a straight line.

Physics Exam Master Sheet: Momentum, Energy, Rotational Motion, Gravity, Projectiles, Solids

Study Guide - Practice Questions

Study Guide - Flashcards