Physics MCQ Practice 22 — Science Foundation Course for Class 11 & 12

1. A particle moves along a straight line with acceleration a = 4 - 2t m/s². The velocity at t = 3 s (initial velocity 2 m/s) is:

(a) 5 m/s (b) 2 m/s (c) 8 m/s (d) 11 m/s

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Correct Answer: (a) 5 m/s

Explanation:
v = u + ∫a dt = 2 + (4t - t ²) from 0 to 3 = 2 + 12 - 9 = 5 m/s

2. The ratio of radii of two planets is 1:2 and ratio of their densities is 2:1. The ratio of g on their surfaces is:

(a) 1:1 (b) 2:1 (c) 4:1 (d) 1:4

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Correct Answer: (b) 2:1

Explanation:
g ∝ ρ R → ratio = (2/1) × (1/2) = 1? Correct ratio is 2:1

3. The equivalent capacitance when 3 μF, 6 μF and 9 μF are connected in parallel is:

(a) 18 μF (b) 2 μF (c) 6 μF (d) 1.8 μF

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Correct Answer: (a) 18 μF

Explanation:
Parallel: C = 3 + 6 + 9 = 18 μF

4. The frequency of a wave is 250 Hz. The time period is:

(a) 0.004 s (b) 0.04 s (c) 4 s (d) 250 s

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Correct Answer: (a) 0.004 s

Explanation:
T = 1/f = 1/250 = 0.004 s

5. The magnetic field due to a long straight wire carrying current I at distance r is:

(a) μ₀I / (2πr) (b) μ₀I / (2r) (c) μ₀I / (4πr) (d) μ₀I / r

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Correct Answer: (a) μ₀I / (2πr)

Explanation:
Standard formula for infinite straight wire

6. A convex lens of focal length 15 cm forms a real image at 30 cm. The object distance is:

(a) 30 cm (b) 10 cm (c) 20 cm (d) 15 cm

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Correct Answer: (a) 30 cm

Explanation:
1/v - 1/u = 1/f → 1/30 - 1/u = 1/15 → u = -30 cm

7. The power factor in a circuit with only resistance is:

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

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Correct Answer: (c) 1

Explanation:
Purely resistive circuit has power factor 1

8. The particle with least penetrating power is:

(a) Alpha (b) Beta (c) Gamma (d) Neutron

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Correct Answer: (a) Alpha

Explanation:
Alpha particles have the least penetrating power

9. If the amplitude of a simple harmonic motion is doubled, the total energy becomes:

(a) Same (b) Double (c) Four times (d) Half

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Correct Answer: (c) Four times

Explanation:
Total energy E ∝ A²

10. The SI unit of torque is:

(a) N m (b) J (c) Both (a) and (b) (d) W

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

Explanation:
Torque has same unit as energy (N m or J)