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

1. A body is dropped from a tower of height 100 m. The velocity with which it hits the ground (g=10 m/s ²) is:

(a) 10 m/s (b) 20 m/s (c) 44.7 m/s (d) 100 m/s

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Correct Answer: (c) 44.7 m/s

Explanation:
v = √(2gh) = √(2×10×100) = √2000 ≈ 44.7 m/s

2. The universal gravitational constant G has the dimensional formula:

(a) [M⁻¹L³T⁻²] (b) [MLT⁻²] (c) [M⁻¹L³T⁻¹] (d) [M²L ³T⁻²]

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Correct Answer: (a) [M⁻¹L³T⁻²]

Explanation:
F = GMm/r² → G = Fr²/Mm → [MLT⁻²][L²]/[M²] = [M⁻¹L³T⁻²]

3. Three capacitors of 3 μF each are connected in series. The equivalent capacitance is:

(a) 9 μF (b) 3 μF (c) 1 μF (d) 6 μF

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Correct Answer: (c) 1 μF

Explanation:
1/C = 1/3 + 1/3 + 1/3 = 1 → C = 1 μF

4. The speed of sound in air is 340 m/s. The minimum frequency of audible sound for a person with 17 cm ear canal (closed pipe) is approximately:

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Correct Answer: (a) 500 Hz

Explanation:
Fundamental frequency f = v/(4L) = 340/(4×0.17) ≈ 500 Hz

5. The magnetic field inside a long solenoid is independent of:

(a) Current (b) Number of turns per unit length (c) Radius of solenoid (d) Permeability of medium

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Correct Answer: (c) Radius of solenoid

Explanation:
B = μ₀ n I (independent of radius)

6. A convex lens forms a real image of an object at 25 cm. If the lens is moved 15 cm away from the object, the image shifts 30 cm. The focal length is:

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

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Correct Answer: (b) 15 cm

Explanation:
Using lens displacement method, f = 15 cm

7. In a series LCR circuit, the resonance frequency is 50 Hz. If L is doubled and C is halved, new resonance frequency is:

(a) 50 Hz (b) 100 Hz (c) 25 Hz (d) 70.7 Hz

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Correct Answer: (b) 100 Hz

Explanation:
f = 1/(2π√(LC)) → new f = 100 Hz

8. The process in which a heavy nucleus splits into two lighter nuclei is called:

(a) Fusion (b) Fission (c) Alpha decay (d) Beta decay

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Correct Answer: (b) Fission

Explanation:
Nuclear fission is splitting of heavy nucleus

9. If the length of a simple pendulum is increased to 4 times, the time period becomes:

(a) Same (b) Double (c) 4 times (d) √2 times

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Correct Answer: (b) Double

Explanation:
T ∝ √L → L becomes 4 times → T becomes 2 times

10. The SI unit of impulse is:

(a) N (b) kg m/s (c) J (d) W

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Correct Answer: (b) kg m/s

Explanation:
Impulse = Force × time = change in momentum → unit kg m/s