Physics MCQ Practice 21 — Science Foundation Course for Class 11 & 12

1. A car starts from rest and reaches 20 m/s in 4 seconds. The acceleration is:

(a) 2 m/s² (b) 5 m/s² (c) 10 m/s² (d) 80 m/s²

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Correct Answer: (b) 5 m/s²

Explanation:
a = (v - u)/t = 20/4 = 5 m/s ²

2. The orbital velocity of a satellite near Earth's surface is 7.9 km/s. The escape velocity is:

(a) 7.9 km/s (b) 11.2 km/s (c) 3.95 km/s (d) 15.8 km/s

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Correct Answer: (b) 11.2 km/s

Explanation:
v_esc = √2 × v_orbital ≈ 1.414 × 7.9 ≈ 11.2 km/s

3. The equivalent capacitance of two 8 μF capacitors in series is:

(a) 16 μF (b) 8 μF (c) 4 μF (d) 2 μF

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Correct Answer: (c) 4 μF

Explanation:
1/C = 1/8 + 1/8 → C = 4 μF

4. The wavelength of a radio wave with frequency 100 MHz (c = 3×10⁸ m/s) is:

(a) 3 m (b) 30 m (c) 300 m (d) 0.3 m

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Correct Answer: (a) 3 m

Explanation:
λ = c/f = 3×10⁸ / 10⁸ = 3 m

5. The force between two parallel current-carrying wires is attractive when currents are:

(a) In same direction (b) In opposite direction (c) Zero (d) Alternating

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Correct Answer: (a) In same direction

Explanation:
Parallel currents in same direction attract

6. A concave mirror of focal length 20 cm forms an image at 40 cm. The object distance is:

(a) 40 cm (b) 20 cm (c) 13.3 cm (d) 80 cm

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Correct Answer: (a) 40 cm

Explanation:
1/v = 1/f - 1/u = -1/20 - 1/(-40) → v = -40 cm

7. In a series LCR circuit, the impedance is minimum at:

(a) Low frequency (b) High frequency (c) Resonance frequency (d) Zero frequency

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Correct Answer: (c) Resonance frequency

Explanation:
Z = R at resonance (minimum)

8. The particle with highest penetrating power is:

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

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Correct Answer: (c) Gamma

Explanation:
Gamma rays have highest penetrating power

9. If the length of a simple pendulum is halved, the time period becomes:

(a) Same (b) Half (c) √2 times (d) 1/√2 times

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Correct Answer: (d) 1/√2 times

Explanation:
T ∝ √L → L/2 → T becomes T/√2

10. The physical quantity with unit kg m²/s is:

(a) Force (b) Momentum (c) Angular momentum (d) Energy

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Correct Answer: (c) Angular momentum

Explanation:
L = Iω or mvr → unit kg m²/s