Physics MCQ Practice 23 — Science Foundation Course for Class 11 & 12

1. A body is projected horizontally with velocity 15 m/s from a height of 20 m. The horizontal range is (g=10 m/s²):

(a) 30 m (b) 60 m (c) 45 m (d) 15 m

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Correct Answer: (a) 30 m

Explanation:
Time of flight t = √(2h/g) = 2 s → Range = 15 × 2 = 30 m

2. The value of g at a depth d below Earth's surface is g' = g(1 - d/R). For d = R/2, g' is:

(a) g/2 (b) g/4 (c) g (d) Zero

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Correct Answer: (a) g/2

Explanation:
g' = g (1 - d/R) = g (1 - 0.5) = g/2

3. The equivalent resistance of 3 Ω, 6 Ω and 9 Ω in series is:

(a) 18 Ω (b) 2 Ω (c) 1 Ω (d) 6 Ω

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Correct Answer: (a) 18 Ω

Explanation:
R = 3 + 6 + 9 = 18 Ω

4. The frequency of a wave is 400 Hz. The time period is:

(a) 0.0025 s (b) 0.025 s (c) 2.5 s (d) 400 s

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Correct Answer: (a) 0.0025 s

Explanation:
T = 1/f = 1/400 = 0.0025 s

5. The direction of magnetic field inside a solenoid is given by:

(a) Right hand thumb rule (b) Left hand thumb rule (c) Fleming’s left hand rule (d) Fleming’s right hand rule

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Correct Answer: (a) Right hand thumb rule

Explanation:
Right hand thumb rule for solenoid

6. A concave mirror has focal length 25 cm. For an object at 50 cm, the image distance is:

(a) 50 cm (b) 25 cm (c) 16.7 cm (d) 33.3 cm

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Correct Answer: (a) 50 cm

Explanation:
1/v = 1/f - 1/u = -1/25 - 1/(-50) = -1/50 → v = -50 cm

7. The power factor of a circuit with only capacitance is:

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

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Correct Answer: (b) 0

Explanation:
Pure capacitive circuit has power factor 0

8. The isotope used in nuclear reactors as fuel is:

(a) U-235 (b) U-238 (c) Th-232 (d) Pu-239

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Correct Answer: (a) U-235

Explanation:
Uranium-235 is the main fissile fuel

9. If the length of a simple pendulum is increased by 21%, the percentage increase in time period is approximately:

(a) 10% (b) 21% (c) 10.5% (d) 42%

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Correct Answer: (c) 10.5%

Explanation:
T ∝ √L → % increase ≈ (1/2) × 21% = 10.5%

10. The physical quantity with unit Newton-second is:

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

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Correct Answer: (a) Impulse

Explanation:
Impulse = F × t = change in momentum