Question 1

Which of the following best distinguishes work from energy in physics?

Accepted Answer

Work, $$W$$, is a process that transfers energy, while energy, $$E$$, is a state function describing the ability to do work.

Question 2

What is the SI unit of both work and energy, and how is it defined in terms of base units?

Accepted Answer

$$1 \ \mathrm{J} = 1 \ \mathrm{kg} \ \mathrm{m}^2 \ \mathrm{s}^{-2}$$

Question 3

A 200-g book is lifted vertically by 30 cm at constant speed. How much work is done by the lifting force? (Assume $$g = 9.8 \ \mathrm{m/s}^2)$$

Accepted Answer

$$0.59 \ \mathrm{J}$$

Question 4

Which of the following statements about work is correct?

Accepted Answer

Work is only done when a force acts on a moving object.

Question 5

A force of $$F = (6\hat{i} - 3\hat{j}) \ \mathrm{N}$$ acts on an object that moves through a displacement of $$\vec{d} = (2\hat{i} + 2\hat{j}) \ \mathrm{m}. $$What is the work done by the force?

Accepted Answer

$$6 \ \mathrm{J}$$

Question 6

If a force acts perpendicular to the direction of motion ($$	heta = 90^\circ$$), what is the work done by the force?

Accepted Answer

$$0$$

Question 7

A variable force $$F = (5 \ \mathrm{N}) x$$^{1/2}$$ acts on an object as it moves from x = 0$ to x = 3$$ \ \mathrm{m}$$. How much work does this force do?

Accepted Answer

$$10 \ \mathrm{J}$$

Question 8

Which of the following best describes kinetic energy?

Accepted Answer

Kinetic energy is the energy of motion, given by $$K = \frac{1}{2} m v^2$.

Question 9

A 500-kg car traveling at $$20 \ \mathrm{m/s}$$ comes to a stop due to a constant braking force of $$5000 \ \mathrm{N}. $$How far does the car travel before stopping?

Accepted Answer

$$40 \ \mathrm{m}$$

Question 10

Which of the following is a correct statement about the sign of work?

Accepted Answer

Positive work adds energy to the system, while negative work removes energy from the system.

Question 11

The net work done on a system is equal to:

Accepted Answer

The sum of the work done by all forces: $$W_{\mathrm{net}} = W_1$ + W_2$ + \ldots$$

Question 12

Which equation correctly expresses the work done by a constant force $$\vec{F}$$ over a displacement $$\Delta \vec{x} at an $$angle $$	heta$$?

Accepted Answer

$$W = F \Delta x \cos 	heta$$

Question 13

A ball is swung in a horizontal circle at constant speed by a string. What is the work done by the tension force in the string during one revolution?

Accepted Answer

$$0$$

Question 14

Which of the following is a nonmechanical form of energy?

Accepted Answer

Thermal energy, $$E_{th}$$

Question 15

If a force $$\vec{F}$$ acts at an angle $$	heta to $$the displacement $$\vec{d}$$, which mathematical operation gives the work done?

Accepted Answer

The scalar (dot) product: $$\vec{F} \cdot \vec{d} = F d \cos 	heta$$

Question 16

Graphically, the work done by a variable force in one dimension is represented by:

Accepted Answer

The area under the $$F$$-$$x$$ graph.

Question 17

Which of the following is true about the relationship between work and kinetic energy?

Accepted Answer

The net work done on an object equals the change in its kinetic energy: $$W = \Delta K$$

Question 18

A 1000-kg elevator accelerates upward at $$1 \ \mathrm{m/s}^2$$ for $$10 \ \mathrm{m}$$, starting from rest. How much work does gravity do on the elevator?

Accepted Answer

$$-98,000 \ \mathrm{J}$$

Question 19

Which of the following is a correct statement about the units of work and energy?

Accepted Answer

Both work and energy have the same SI unit: the joule ($$\mathrm{J}).$$

Work and Energy in Physics: Concepts, Calculations, and Applications

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