AP Physics AP Physics Fluid Mechanics & Energy Systems 2 — Questions and Answers
Question 1: The work-energy theorem states that the net work done on an object equals:
- Its potential energy
- Its change in kinetic energy (Correct answer)
- Its total mechanical energy
- The product of force and time
Correct answer: Its change in kinetic energy
The work-energy theorem states W_net = ΔKE, the net work equals the change in kinetic energy.
Question 2: A 2 kg object is lifted 5 m. How much gravitational potential energy is gained? (g = 10 m/s²)
- 10 J
- 25 J
- 100 J (Correct answer)
- 50 J
Correct answer: 100 J
ΔPE = mgh = 2 × 10 × 5 = 100 J.
Question 3: In a conservative system, as an object falls and speeds up, mechanical energy:
- Increases
- Decreases
- Is converted from potential to kinetic (Correct answer)
- Disappears
Correct answer: Is converted from potential to kinetic
In a conservative system, total mechanical energy is conserved; potential energy converts to kinetic energy as the object falls.
Question 4: A spring with spring constant k = 200 N/m is compressed 0.1 m. What is the elastic potential energy stored?
- 20 J
- 1 J (Correct answer)
- 10 J
- 2 J
Correct answer: 1 J
Elastic PE = (1/2)kx² = (1/2)(200)(0.1)² = 1 J.
Question 5: Power is defined as:
- Force times distance
- Work times time
- Work divided by time (Correct answer)
- Energy times velocity
Correct answer: Work divided by time
Power P = W/t, the rate at which work is done or energy is transferred.
Question 6: A 60 W motor lifts a 30 N load at constant speed. How fast does it lift the load?
- 0.5 m/s
- 1800 m/s
- 2 m/s (Correct answer)
- 30 m/s
Correct answer: 2 m/s
P = Fv, so v = P/F = 60/30 = 2 m/s.
AP Physics AP Physics Fluid Mechanics & Energy Systems 2
The work-energy theorem states that the net work done on an object equals: