Work and Energy Part 1: MCQs (Q1–Q25)
⚡ Work and Energy – Class 9 Science MCQs
Section 1: Work – Definition, Conditions & Basic Concepts (Q1–Q25)
Q1. Work is said to be done when:
A. Force is applied
B. Body is displaced
C. Force and displacement have a component in same direction
D. Only displacement occurs
✅ Correct Answer: C. Force and displacement have a component in same direction
Explanation:
- A. Force alone is not enough.
- B. Displacement alone is not enough.
- C. Correct, both force and displacement must act in same direction (or component).
- D. Wrong, no force → no work.
Q2. Work is zero when:
A. Force = 0
B. Displacement = 0
C. Force ⟂ displacement
D. All of these
✅ Correct Answer: D. All of these
Q3. SI unit of work is:
A. Watt
B. Newton
C. Joule
D. Erg
✅ Correct Answer: C. Joule
Explanation:
- 1 Joule = 1 Newton × 1 metre displacement in direction of force.
Q4. 1 Joule of work is done when:
A. 1 N force moves body by 1 m
B. 1 kg body moves with velocity 1 m/s
C. 1 N force moves body by 1 cm
D. 1 kg body lifted by 1 cm
✅ Correct Answer: A. 1 N force moves body by 1 m
Q5. Work is positive when:
A. Force and displacement are in opposite directions
B. Force and displacement are in same direction
C. No displacement occurs
D. Force is perpendicular to displacement
✅ Correct Answer: B. Force and displacement are in same direction
Q6. Work is negative when:
A. Displacement is zero
B. Force is perpendicular to displacement
C. Force opposes displacement
D. Force is absent
✅ Correct Answer: C. Force opposes displacement
Q7. Which of these involves zero work?
A. A boy pushing wall
B. A book lying on table
C. Moon revolving around Earth
D. All of these
✅ Correct Answer: D. All of these
Explanation:
- In all cases, either no displacement or force ⟂ displacement.
Q8. Work done by gravity on object falling freely is:
A. Positive
B. Negative
C. Zero
D. Cannot say
✅ Correct Answer: A. Positive
Explanation:
- Force of gravity acts downward, displacement is downward.
Q9. Work done by frictional force is usually:
A. Positive
B. Negative
C. Zero
D. Infinite
✅ Correct Answer: B. Negative
Explanation:
- Friction opposes motion.
Q10. Work done when force = 0 is:
A. Zero
B. Infinite
C. Negative
D. Positive
✅ Correct Answer: A. Zero
Q11. Work done by centripetal force in circular motion is:
A. Positive
B. Negative
C. Zero
D. Maximum
✅ Correct Answer: C. Zero
Explanation:
- Force is always perpendicular to displacement in circular motion.
Q12. Formula for work =
A. W = F × d
B. W = F × d × cos θ
C. W = m × g × h
D. W = F/t
✅ Correct Answer: B. W = F × d × cos θ
Explanation:
- Work depends on angle between force and displacement.
Q13. A porter carrying load on head walks horizontally. Work done against gravity is:
A. Positive
B. Negative
C. Zero
D. Cannot say
✅ Correct Answer: C. Zero
Explanation:
- Force of gravity is vertical, displacement horizontal → cos 90° = 0.
Q14. A coolie applies force on suitcase vertically upward while moving on horizontal road. Work done = ?
A. Positive
B. Negative
C. Zero
D. Cannot say
✅ Correct Answer: C. Zero
Q15. Work done on body depends on:
A. Magnitude of force
B. Displacement
C. Angle between force and displacement
D. All of these
✅ Correct Answer: D. All of these
Q16. If a body is displaced 5 m by a force of 10 N acting at 60°, work done = ?
A. 25 J
B. 50 J
C. 30 J
D. 20 J
✅ Correct Answer: C. 25 J
Explanation:
- W = F d cos θ = 10 × 5 × cos 60° = 50 × 0.5 = 25 J.
Q17. A boy lifts a 20 kg mass to height 2 m. Work done = ? (g = 10 m/s²)
A. 200 J
B. 300 J
C. 400 J
D. 500 J
✅ Correct Answer: C. 400 J
Explanation:
- W = mgh = 20 × 10 × 2 = 400 J.
Q18. Which of the following is not work?
A. Lifting a bag
B. Writing with pen
C. Sleeping on bed
D. Pushing a cart
✅ Correct Answer: C. Sleeping on bed
Explanation:
- No force or displacement.
Q19. Work is a:
A. Scalar quantity
B. Vector quantity
C. Both
D. None
✅ Correct Answer: A. Scalar quantity
Explanation:
- Work = F d cos θ → no direction, only magnitude.
Q20. A boy applies force 100 N on wall, but wall does not move. Work = ?
A. 0 J
B. 100 J
C. 200 J
D. Cannot say
✅ Correct Answer: A. 0 J
Explanation:
- Displacement = 0 → work = 0.
Q21. A ball is thrown upwards. Work done by gravity is:
A. Positive
B. Negative
C. Zero
D. Constant
✅ Correct Answer: B. Negative
Explanation:
- Force downward, displacement upward → opposite direction.
Q22. Work done by normal force of table on book lying on it is:
A. Positive
B. Negative
C. Zero
D. Constant
✅ Correct Answer: C. Zero
Q23. The angle between force and displacement for maximum work:
A. 0°
B. 90°
C. 180°
D. 360°
✅ Correct Answer: A. 0°
Explanation:
- cos 0° = 1 → maximum work.
Q24. Work done in lifting 10 N weight through 10 m:
A. 100 J
B. 200 J
C. 50 J
D. 0 J
✅ Correct Answer: A. 100 J
Explanation:
- W = F × d = 10 × 10 = 100 J.
Q25. Work done when displacement is perpendicular to force = ?
A. Maximum
B. Minimum
C. Zero
D. Infinite
✅ Correct Answer: C. Zero
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