WTMA Energy, Work, and Power 4 — Questions and Answers
Question 1: Water stored behind a dam is an example of which type of energy?
- Kinetic energy
- Thermal energy
- Gravitational potential energy (Correct answer)
- Nuclear energy
Correct answer: Gravitational potential energy
Water elevated behind a dam has gravitational potential energy due to its height above the turbines below.
Question 2: A 60-watt light bulb runs for 2 hours. How much energy does it consume?
- 120 watt-hours (Correct answer)
- 30 watt-hours
- 60 watt-hours
- 240 watt-hours
Correct answer: 120 watt-hours
Energy = Power × Time = 60 W × 2 h = 120 watt-hours.
Question 3: In a pulley system, a worker pulls 6 feet of rope to raise a load 2 feet. What is the mechanical advantage?
- 2
- 3 (Correct answer)
- 6
- 12
Correct answer: 3
Mechanical advantage = effort distance / load distance = 6 / 2 = 3.
Question 4: What happens to the potential energy of a roller coaster car as it descends a hill (ignoring friction)?
- It increases
- It remains the same
- It converts to kinetic energy (Correct answer)
- It converts to thermal energy
Correct answer: It converts to kinetic energy
As the car descends, gravitational potential energy converts to kinetic energy, increasing the car's speed.
Question 5: Which of the following actions requires the most power?
- Lifting 100 lbs 10 feet in 10 seconds
- Lifting 100 lbs 10 feet in 5 seconds (Correct answer)
- Lifting 50 lbs 10 feet in 5 seconds
- Lifting 50 lbs 5 feet in 10 seconds
Correct answer: Lifting 100 lbs 10 feet in 5 seconds
Power = Work/Time; 100×10/5 = 200 ft-lb/s is the highest among all choices.
Question 6: A flywheel spins at high speed to store energy. This is an example of:
- Chemical potential energy
- Rotational kinetic energy (Correct answer)
- Elastic potential energy
- Nuclear energy
Correct answer: Rotational kinetic energy
A spinning flywheel stores rotational kinetic energy, which can be released to do work.
Question 7: Which factor does NOT affect how much work is done when pushing a box across a floor?
- The force applied
- The distance moved
- The color of the box (Correct answer)
- The direction of the force
Correct answer: The color of the box
Work = Force × Distance × cos(θ); the color of the box has no effect on work done.
WTMA Energy, Work, and Power 4
Water stored behind a dam is an example of which type of energy?