Bennett Mechanical Test Bennett Mechanical Work and Energy Questions and Answers 2 — Questions and Answers
Question 1: A 1000 W motor runs for 30 seconds. How much energy does it consume?
- 300 J
- 3,000 J
- 30,000 J (Correct answer)
- 30 J
Correct answer: 30,000 J
Energy = Power × time = 1000 × 30 = 30,000 J.
Question 2: Which form of energy is stored in a stretched rubber band?
- Kinetic energy
- Thermal energy
- Chemical energy
- Elastic potential energy (Correct answer)
Correct answer: Elastic potential energy
A stretched rubber band stores elastic potential energy due to its deformation.
Question 3: A 2 kg object moves at 4 m/s. What is its kinetic energy?
- 8 J
- 16 J (Correct answer)
- 32 J
- 4 J
Correct answer: 16 J
KE = ½mv² = ½ × 2 × 4² = 16 J.
Question 4: According to the law of conservation of energy, what happens to total energy in a closed system?
- It increases
- It decreases
- It remains constant (Correct answer)
- It doubles
Correct answer: It remains constant
Energy cannot be created or destroyed; it only changes form, so total energy in a closed system is constant.
Question 5: A 60 W light bulb operates for 2 hours. How much energy does it consume?
- 120 J
- 7,200 J
- 432,000 J (Correct answer)
- 60 J
Correct answer: 432,000 J
Energy = 60 W × (2 × 3600 s) = 60 × 7200 = 432,000 J.
Question 6: Work is only done on an object when an applied force causes what?
- A temperature change
- An increase in mass
- Displacement (Correct answer)
- Vibration
Correct answer: Displacement
Work requires both a force and displacement in the direction of that force; no movement means no work.
Bennett Mechanical Test Bennett Mechanical Work and Energy Questions and Answers 2
A 1000 W motor runs for 30 seconds.
How much energy does it consume?