Physics MCQ Practice 26 — Science Foundation Course for Class 11 & 12

1. A body is projected vertically upward with velocity 30 m/s. The time to return to the point of projection (g=10 m/s²) is:

(a) 3 s (b) 6 s (c) 4 s (d) 12 s

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Correct Answer: (b) 6 s

Explanation:
Time of flight = 2u/g = 60/10 = 6 s

2. The gravitational field intensity at a distance r from the centre of Earth (r > R) is:

(a) GM/r² (b) GM/r (c) gR ²/r² (d) Both (a) and (c)

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Correct Answer: (d) Both (a) and (c)

Explanation:
g' = GM/r² = g (R/r)²

3. The equivalent capacitance of three 6 μF capacitors in parallel is:

(a) 18 μF (b) 2 μF (c) 6 μF (d) 3 μF

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Correct Answer: (a) 18 μF

Explanation:
Parallel: C = 6 + 6 + 6 = 18 μF

4. The frequency of a wave is 1000 Hz. The time period is:

(a) 0.001 s (b) 0.01 s (c) 1 s (d) 1000 s

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Correct Answer: (a) 0.001 s

Explanation:
T = 1/f = 0.001 s

5. The magnetic field inside a long solenoid carrying current I with n turns per unit length is:

(a) μ₀ n I (b) μ₀ I / (2πr) (c) μ₀ I / (2r) (d) Zero

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Correct Answer: (a) μ₀ n I

Explanation:
B = μ₀ n I inside solenoid

6. A convex lens of focal length 30 cm forms a real image at 60 cm. The object distance is:

(a) 60 cm (b) 20 cm (c) 30 cm (d) 15 cm

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Correct Answer: (a) 60 cm

Explanation:
1/v - 1/u = 1/f → 1/60 - 1/u = 1/30 → u = -60 cm

7. The power factor in a circuit with R, L and C at resonance is:

(a) 0 (b) 0.5 (c) 1 (d) Infinite

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Correct Answer: (c) 1

Explanation:
At resonance, power factor = 1

8. The coolant used in nuclear reactors is usually:

(a) Water (b) Heavy water (c) Liquid sodium (d) All of the above

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Correct Answer: (d) All of the above

Explanation:
Different reactors use different coolants

9. If the length of a simple pendulum is increased by 9%, the percentage increase in time period is:

(a) 4.5% (b) 9% (c) 18% (d) 2.25%

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Correct Answer: (a) 4.5%

Explanation:
T ∝ √L → 9% increase in L → 4.5% increase in T

10. The physical quantity with unit kg m/s² is:

(a) Force (b) Momentum (c) Energy (d) Power

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Correct Answer: (a) Force

Explanation:
Force = mass × acceleration = kg m/s² = Newton