Q: Jon pulls a box with a force of $50.0\ \mathrm{N}$ at an angle of $20.0^\circ$ above the horizontal for a distance of $3.0\ \mathrm{m}$. What is the work done by Jon on the box?

$W = 50.0 \times 3.0 \times \cos(20.0^\circ) = 140.9\ \mathrm{J}$

Q: A $7.00\ \mathrm{kg}$ ball is held and then dropped from rest. What is its kinetic energy just before it hits the ground if it falls $3.00\ \mathrm{m}$?

$KE = mgh = 7.00 \times 9.8 \times 3.00 = 205.8\ \mathrm{J}$

Q: A $2.00\ \mathrm{kg}$ object is moving at $3.00\ \mathrm{m/s}$. What is its kinetic energy?

$KE = \frac{1}{2} \times 2.00 \times (3.00)^2 = 9.0\ \mathrm{J}$

Q: If a force of $60.0\ \mathrm{N}$ is applied over a distance of $3.0\ \mathrm{m}$ at an angle of $18^\circ$ to the direction of motion, what is the work done?

$W = 60.0 \times 3.0 \times \cos(18^\circ) = 171.0\ \mathrm{J}$

Q: A $1.00\ \mathrm{kg}$ object moves at $3.00\ \mathrm{m/s}$. What is its kinetic energy?

$KE = \frac{1}{2} \times 1.00 \times (3.00)^2 = 4.5\ \mathrm{J}$

Q: A $10.0\ \mathrm{kg}$ object is lifted to a height of $4.34\ \mathrm{m}$. What is its gravitational potential energy?

$PE = 10.0 \times 9.8 \times 4.34 = 425.3\ \mathrm{J}$

Q: A spring with spring constant $k = 200\ \mathrm{N/m}$ is compressed by $0.08\ \mathrm{m}$. What is the elastic potential energy stored in the spring?

$PE = \frac{1}{2} \times 200 \times (0.08)^2 = 0.64\ \mathrm{J}$

Q: A $3.00\ \mathrm{kg}$ object is dropped from a height of $5.00\ \mathrm{m}$. What is its speed just before hitting the ground? (Assume $g = 9.8\ \mathrm{m/s^2}$)

$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 5.00} = 9.9\ \mathrm{m/s}$

Question 1

Jon pulls a box with a force of $50.0\ \mathrm{N}$ at an angle of $20.0^\circ$ above the horizontal for a distance of $3.0\ \mathrm{m}$. What is the work done by Jon on the box?

Accepted Answer

$W = 50.0 	imes 3.0 	imes \cos(20.0^\circ) = 140.9\ \mathrm{J}$

Question 2

A $7.00\ \mathrm{kg}$ ball is held and then dropped from rest. What is its kinetic energy just before it hits the ground if it falls $3.00\ \mathrm{m}$?

Accepted Answer

$KE = mgh = 7.00 	imes 9.8 	imes 3.00 = 205.8\ \mathrm{J}$

Question 3

Which equation correctly expresses the work-energy theorem?

Accepted Answer

$W = \Delta KE$

Question 4

A $2.00\ \mathrm{kg}$ object is moving at $3.00\ \mathrm{m/s}$. What is its kinetic energy?

Accepted Answer

$KE = \frac{1}{2} 	imes 2.00 	imes (3.00)^2 = 9.0\ \mathrm{J}$

Question 5

If a force of $60.0\ \mathrm{N}$ is applied over a distance of $3.0\ \mathrm{m}$ at an angle of $18^\circ$ to the direction of motion, what is the work done?

Accepted Answer

$W = 60.0 	imes 3.0 	imes \cos(18^\circ) = 171.0\ \mathrm{J}$

Question 6

Which of the following best describes mechanical energy?

Accepted Answer

The sum of kinetic and potential energy in a system.

Question 7

A $1.00\ \mathrm{kg}$ object moves at $3.00\ \mathrm{m/s}$. What is its kinetic energy?

Accepted Answer

$KE = \frac{1}{2} 	imes 1.00 	imes (3.00)^2 = 4.5\ \mathrm{J}$

Question 8

Which formula is used to calculate gravitational potential energy?

Accepted Answer

$PE = mgh$

Question 9

A $10.0\ \mathrm{kg}$ object is lifted to a height of $4.34\ \mathrm{m}$. What is its gravitational potential energy?

Accepted Answer

$PE = 10.0 	imes 9.8 	imes 4.34 = 425.3\ \mathrm{J}$

Question 10

A spring with spring constant $k = 200\ \mathrm{N/m}$ is compressed by $0.08\ \mathrm{m}$. What is the elastic potential energy stored in the spring?

Accepted Answer

$PE = \frac{1}{2} 	imes 200 	imes (0.08)^2 = 0.64\ \mathrm{J}$

Question 11

Which of the following scenarios best illustrates the conservation of mechanical energy?

Accepted Answer

A pendulum swinging without air resistance.

Question 12

A $3.00\ \mathrm{kg}$ object is dropped from a height of $5.00\ \mathrm{m}$. What is its speed just before hitting the ground? (Assume $g = 9.8\ \mathrm{m/s^2}$)

Accepted Answer

$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 5.00} = 9.9\ \mathrm{m/s}$

Question 13

Which of the following is NOT a form of potential energy?

Accepted Answer

Kinetic energy

Question 14

A $5.00\ \mathrm{kg}$ object is moving at $4.00\ \mathrm{m/s}$. What is its kinetic energy?

Accepted Answer

$KE = \frac{1}{2} 	imes 5.00 	imes (4.00)^2 = 40.0\ \mathrm{J}$

Question 15

A $2.00\ \mathrm{kg}$ ball is thrown vertically upward with a speed of $6.00\ \mathrm{m/s}$. What is its maximum height?

Accepted Answer

$h = \frac{v^2}{2g} = \frac{(6.00)^2}{2 	imes 9.8} = 1.84\ \mathrm{m}$

Question 16

Which of the following statements about the work-energy theorem is correct?

Accepted Answer

The net work done on an object equals its change in kinetic energy.

Question 17

A $4.00\ \mathrm{kg}$ object is lifted $2.00\ \mathrm{m}$ above the ground. What is its gravitational potential energy?

Accepted Answer

$PE = 4.00 	imes 9.8 	imes 2.00 = 78.4\ \mathrm{J}$

Question 18

A $3.00\ \mathrm{kg}$ object is moving at $5.00\ \mathrm{m/s}$. What is its kinetic energy?

Accepted Answer

$KE = \frac{1}{2} 	imes 3.00 	imes (5.00)^2 = 37.5\ \mathrm{J}$

Work, Energy, and Mechanical Energy in Physics

Study Guide - Practice Questions

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