BECE Force, Work, and Energy 2 — Questions and Answers
Question 1: A block is pushed across a floor with a force of 20 N over a distance of 5 m. How much work is done on the block?
- 25 J
- 100 J (Correct answer)
- 4 J
- 15 J
Correct answer: 100 J
Work = Force × distance = 20 N × 5 m = 100 J.
Question 2: Which of the following is a non-contact force?
- Friction
- Normal reaction
- Gravitational force (Correct answer)
- Tension
Correct answer: Gravitational force
Gravitational force acts between objects without physical contact, making it a non-contact force.
Question 3: A 5 kg object is lifted 3 m vertically. If g = 10 m/s², what is the gravitational potential energy gained?
- 15 J
- 8 J
- 150 J (Correct answer)
- 50 J
Correct answer: 150 J
GPE = mgh = 5 × 10 × 3 = 150 J.
Question 4: Which unit is used to measure work?
- Newton
- Watt
- Joule (Correct answer)
- Pascal
Correct answer: Joule
Work is measured in Joules (J), which equals Newton-metres (N·m).
Question 5: A 2 kg ball moving at 4 m/s comes to rest after hitting a wall. How much kinetic energy did it lose?
- 8 J
- 4 J
- 16 J (Correct answer)
- 32 J
Correct answer: 16 J
KE lost = ½mv² = ½ × 2 × 4² = ½ × 2 × 16 = 16 J.
Question 6: Which of Newton's laws states that every action has an equal and opposite reaction?
- First law
- Second law
- Third law (Correct answer)
- Law of gravitation
Correct answer: Third law
Newton's Third Law states that for every action force there is an equal and opposite reaction force.
Question 7: A machine does 600 J of work in 30 seconds. What is its power output?
- 30 W
- 20 W (Correct answer)
- 18,000 W
- 2 W
Correct answer: 20 W
Power = Work/time = 600 J ÷ 30 s = 20 W.
BECE Force, Work, and Energy 2
A block is pushed across a floor with a force of 20 N over a distance of 5 m.
How much work is done on the block?