Name: _____________________________
ELesson2: Work and Power Problems
Date: ___________
Period: _________
Work and Power
𝑾 = 𝑭𝒅𝒄𝒐𝒔(𝜽)
𝑷𝒐𝒘𝒆𝒓 =
𝑾𝒐𝒓𝒌
𝒕𝒊𝒎𝒆
Work Problems
1. Heather and Minh are arguing about the units of work. Minh says that the units of work are
Newton-meters, but Heather thinks that the units of work are in Joules. Which of them is right?
Explain your answer. What are your assumptions?
2. Sara is waiting in the security line at the airport and has to keep picking up her suitcase, moving
forward, and setting it down again. Calculate the work done by Sara on her 15-kg suitcase in the
following scenarios:
a. When slowly lifting it 0.80 m upward,
b. When holding it and slowly moving forward 1.0 m, and
c. When lowering it 0.80 m down again.
3. Komila is pulling a sled up a hill that makes a 24 angle with the horizontal. She keeps the rope
parallel to the hill and exerts a 150-N force on it. How much work will she do if she pulls the sled
150 m?
4. A 4 kg grocery cart rolls down a 3 m long incline with an angle of 10°. How much work does
Earth do on the cart?
5. Juan pushes a box at an angle to the horizontal, doing 250 J of work over a distance of 10 m. If
the force exerted is 30 N, what is the angle between the force exerted by Juan on the box and
the horizontal?
6. To clean the floor, David exerts a 40 N force on a broom handle to push it 2 m. If the broom
handle makes a 40° angle with the floor, what is the work done by David on the broom? If the
broom handle were angled at 65° would David do more or less work? Explain your answer.
7. Tara pushes a baby carriage at an angle 35° to the horizontal over a distance of 20 m on her way
to the playground. If she does 600 J of work on the carriage, what force does she have to exert
on the carriage?
8. Dustin exerts 200 N of force on a box sitting on a horizontal surface. He does not do any work
on the box. How is this possible? Explain your answer.
Power Problems
9. Corrine is training for the annual javelin throwing contest. Determine how much power she
exerts while lifting the following objects. Draw a picture of the initial and final states.
a. a 1.5-kg javelin 1.0 m in 1.0 s
b. a 1.5-kg javelin 1.0 m in 0.5 s
c. a 1.0-kg javelin 2.0 m in 1.0 s
d. a 2.0-kg javelin 1.0 m in 1.0 s
10. There are two types of light bulbs, incandescent and CFLs. Incandescent light bulbs are
commonly rated at 60 Watts. CFL bulbs are rated at 14 Watts.
a. In one minute how many Joules of energy would be converted for each bulb? In one
hour?
b. If you are charged $0.11 per Kilowatt●Hr estimate how much money you could save per
year using a CFL compared to an incandescent light bulb. What assumptions did you
make in your calculations?
11. The luminosity of the Sun is the amount of power the Sun emits in the form of electromagnetic
radiation. The Sun’s luminosity is 3.8 x 1026 W. If you were able to collect all of the Sun’s energy,
estimate how long you have to collect it in order to light all of Earth’s light bulbs. Explain how
you came to this conclusion.