⚡ Work and Energy – Class 9 Science MCQs

Section 2: Energy – Kinetic, Potential & Work-Energy Theorem (Q26–Q50)

Q26. Energy is defined as:

A. Rate of doing work
B. Capacity to do work
C. Force × distance
D. Work × time

✅ Correct Answer: B. Capacity to do work

Explanation:

• A. Power = rate of doing work.
• B. Correct, energy is ability to perform work.
• C. That’s definition of work.
• D. Incorrect.

Q27. SI unit of energy is:

A. Newton
B. Joule
C. Watt
D. Pascal

✅ Correct Answer: B. Joule

Explanation:

• 1 Joule = work done when 1 N force displaces body 1 m.

Q28. Kinetic energy depends on:

A. Mass
B. Velocity
C. Both mass and velocity
D. Acceleration

✅ Correct Answer: C. Both mass and velocity

Explanation:

• KE = ½ mv².

Q29. Expression for kinetic energy:

A. mgh
B. ½ mv²
C. F × d
D. mgR

✅ Correct Answer: B. ½ mv²

Q30. Potential energy of a body is due to:

A. Its motion
B. Its mass only
C. Its position or configuration
D. Its volume

✅ Correct Answer: C. Its position or configuration

Q31. Expression for potential energy:

A. ½ mv²
B. mgh
C. F × d
D. P × t

✅ Correct Answer: B. mgh

Q32. A body of mass 2 kg moving with velocity 3 m/s. Kinetic energy = ?

A. 6 J
B. 9 J
C. 12 J
D. 18 J

✅ Correct Answer: B. 9 J

Explanation:

• KE = ½ mv² = 0.5 × 2 × 9 = 9 J.

Q33. A body of mass 1 kg raised to height 10 m. Potential energy = ? (g = 10 m/s²)

A. 50 J
B. 100 J
C. 150 J
D. 200 J

✅ Correct Answer: B. 100 J

Explanation:

• PE = mgh = 1 × 10 × 10 = 100 J.

Q34. KE of a body moving with 2 m/s is 100 J. Mass of body = ?

A. 25 kg
B. 50 kg
C. 100 kg
D. 200 kg

✅ Correct Answer: B. 50 kg

Explanation:

• KE = ½ mv² → 100 = 0.5 × m × 4 → m = 50 kg.

Q35. Potential energy of body on ground is:

A. Infinite
B. Zero
C. Maximum
D. Negative

✅ Correct Answer: B. Zero

Explanation:

• Reference level chosen at ground, PE = 0 there.

Q36. Which type of energy is in stretched spring?

A. Kinetic
B. Potential
C. Chemical
D. Heat

✅ Correct Answer: B. Potential

Q37. Work-energy theorem states:

A. Work done = change in KE
B. Work done = KE
C. Work done = change in PE
D. Work done = force × time

✅ Correct Answer: A. Work done = change in KE

Q38. A moving car possesses:

A. Only PE
B. Only KE
C. Both KE and PE
D. No energy

✅ Correct Answer: B. Only KE

Q39. A raised hammer possesses:

A. KE
B. PE
C. Both
D. None

✅ Correct Answer: B. PE

Q40. An object of mass m has velocity doubled. Its kinetic energy becomes:

A. 2 times
B. 3 times
C. 4 times
D. 8 times

✅ Correct Answer: C. 4 times

Explanation:

• KE ∝ v².

Q41. Work done on body = 50 J. This energy is stored as:

A. Power
B. Force
C. Potential or kinetic energy
D. Heat only

✅ Correct Answer: C. Potential or kinetic energy

Q42. Energy possessed by flowing water is:

A. Kinetic
B. Potential
C. Heat
D. Both A and B

✅ Correct Answer: D. Both A and B

Q43. KE of 5 kg body moving at 2 m/s = ?

A. 5 J
B. 10 J
C. 15 J
D. 20 J

✅ Correct Answer: B. 10 J

Explanation:

• KE = ½ × 5 × 4 = 10 J.

Q44. If work done on body is positive, then:

A. KE decreases
B. KE increases
C. KE constant
D. KE = 0

✅ Correct Answer: B. KE increases

Q45. Kinetic energy is always:

A. Positive
B. Negative
C. Zero
D. Infinite

✅ Correct Answer: A. Positive

Q46. Which of the following has only potential energy?

A. Flying bird
B. Stretched bow
C. Moving car
D. Rolling ball

✅ Correct Answer: B. Stretched bow

Q47. Unit of power is:

A. Joule
B. Watt
C. Newton
D. Joule/second

✅ Correct Answer: B. Watt

Explanation:

• Power = work/time, unit Watt = 1 J/s.

Q48. Energy due to position of body is called:

A. Kinetic energy
B. Potential energy
C. Mechanical energy
D. Chemical energy

✅ Correct Answer: B. Potential energy

Q49. Work-energy theorem connects:

A. Work and force
B. Work and displacement
C. Work and KE
D. Work and PE

✅ Correct Answer: C. Work and KE

Q50. Mechanical energy of body =

A. KE only
B. PE only
C. KE + PE
D. Work × time

✅ Correct Answer: C. KE + PE

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