Q: A box is pushed across the floor by a force $\vec{F}$ at an angle $\theta$ to the direction of displacement $\Delta x$. Which equation correctly calculates the work done by the force?

$W = F \cdot \Delta x \cdot \cos(\theta)$

Q: If a 50 kg crate is pulled 40 m along a horizontal floor by a constant force of 100 N, while a frictional force of 50 N opposes the motion, what is the net work done on the crate?

$W_{net} = (100 \text{ N} - 50 \text{ N}) \times 40 \text{ m} = 2000 \text{ J}$

Q: A force varies as $F(x) = 2x$ N, where $x$ is in meters. How much work is done by this force as an object moves from $x = 0$ m to $x = 3$ m?

$W = \int_0^3 2x \, dx = 9 \text{ J}$

Q: A spring with $k = 360 \text{ N/m}$ is compressed by $0.11 \text{ m}$. What is the work done to compress the spring?

$W = \frac{1}{2} \times 360 \times (0.11)^2 = 2.178 \text{ J}$

Q: A video camera arm moves from $x_i = 0.010 \text{ m}$ to $x_f = 0.050 \text{ m}$ under a force $F(x) = 2x$. What is the total work done by the force?

$W = \int_{0.010}^{0.050} 2x \, dx = 0.0016 \text{ J}$

Question 1

Which of the following best describes the physical definition of work in physics?

Accepted Answer

Work is the product of force and displacement in the direction of the force.

Question 2

A box is pushed across the floor by a force $\vec{F}$ at an angle $	heta$ to the direction of displacement $\Delta x$. Which equation correctly calculates the work done by the force?

Accepted Answer

$W = F \cdot \Delta x \cdot \cos(	heta)$

Question 3

If a 50 kg crate is pulled 40 m along a horizontal floor by a constant force of 100 N, while a frictional force of 50 N opposes the motion, what is the net work done on the crate?

Accepted Answer

$W_{net} = (100 	ext{ N} - 50 	ext{ N}) 	imes 40 	ext{ m} = 2000 	ext{ J}$

Question 4

Which force does NOT do work on a box being pulled horizontally across a floor?

Accepted Answer

The normal force perpendicular to the displacement

Question 5

A piano is moved 9 m down a 25° incline and kept from accelerating by a person pushing up the ramp. What is the work done by the person if the force is applied directly opposite to the displacement?

Accepted Answer

$W = F \cdot d \cdot \cos(180°)$

Question 6

Which statement about work and energy is correct?

Accepted Answer

Work is a scalar quantity, and energy is also a scalar quantity.

Question 7

A force varies as $F(x) = 2x$ N, where $x$ is in meters. How much work is done by this force as an object moves from $x = 0$ m to $x = 3$ m?

Accepted Answer

$W = \int_0^3 2x \, dx = 9 	ext{ J}$

Question 8

According to Hooke's Law, what is the restoring force $F$ of a spring displaced by $\Delta x$ from its equilibrium position?

Accepted Answer

$F = -k \Delta x$

Question 9

How much work is required to compress a spring with spring constant $k$ from its equilibrium position by a distance $x$?

Accepted Answer

$W = \frac{1}{2}kx^2$

Question 10

A 1000 kg car traveling at 15 m/s can brake to a stop in 20 m. If another car of the same mass is traveling at 30 m/s, what is its stopping distance assuming the same braking force?

Accepted Answer

80 m

Question 11

Which of the following is the correct expression for the work-energy theorem?

Accepted Answer

$W = \Delta KE = \frac{1}{2}mv_f^2 - \frac{1}{2}mv_i^2$

Question 12

A spring with $k = 360 	ext{ N/m}$ is compressed by $0.11 	ext{ m}$. What is the work done to compress the spring?

Accepted Answer

$W = \frac{1}{2} 	imes 360 	imes (0.11)^2 = 2.178 	ext{ J}$

Question 13

If a force is perpendicular to the displacement of an object, what is the work done by that force?

Accepted Answer

Zero work

Question 14

A force $F$ acts on an object at an angle $	heta$ to the direction of displacement $\Delta x$. For which value of $	heta$ is the work done by the force maximized?

Accepted Answer

$	heta = 0^\circ$

Question 15

A video camera arm moves from $x_i = 0.010 	ext{ m}$ to $x_f = 0.050 	ext{ m}$ under a force $F(x) = 2x$. What is the total work done by the force?

Accepted Answer

$W = \int_{0.010}^{0.050} 2x \, dx = 0.0016 	ext{ J}$

Question 16

Which of the following statements about frictional force is correct?

Accepted Answer

Frictional force does negative work when opposing motion.

Question 17

A spring is compressed from $x = 0$ to $x = 0.07 	ext{ m}$ with $k = 360 	ext{ N/m}$. What is the kinetic energy of a 1.85 kg object released from the spring at $x = 0.07 	ext{ m}$?

Accepted Answer

$KE = \frac{1}{2} 	imes 360 	imes (0.07)^2 = 0.882 	ext{ J}$

Question 18

Which of the following is the SI unit of work and energy?

Accepted Answer

Joule ($	ext{J}$)

Work and Energy: Chapter 7 Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards