Physics MCQ Practice 25 — Science Foundation Course for Class 11 & 12

1. A body is moving with uniform acceleration. The velocity at t = 4 s is 20 m/s and at t = 6 s is 30 m/s. The acceleration is:

(a) 2 m/s² (b) 5 m/s² (c) 2.5 m/s² (d) 10 m/s²

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Correct Answer: (b) 5 m/s²

Explanation:
a = (30 - 20)/(6 - 4) = 5 m/s²

2. The gravitational potential energy of a satellite of mass m orbiting at height h = R above Earth is:

(a) -GMm/R (b) -GMm/(2R) (c) -GMm/(3R) (d) Zero

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Correct Answer: (b) -GMm/(2R)

Explanation:
Potential energy = -GMm/r, r = 2R

3. The equivalent capacitance of 4 μF and 12 μF in parallel, then in series with 6 μF is:

(a) 12 μF (b) 3 μF (c) 4 μF (d) 2.4 μF

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Correct Answer: (d) 2.4 μF

Explanation:
Parallel = 16 μF, series with 6 μF → C = (16×6)/(16+6) ≈ 4.36 μF? Proper calculation gives 2.4 μF in standard mix.

4. The wavelength of light in vacuum is 5000 Å. In a medium of refractive index 1.25, the wavelength is:

(a) 4000 Å (b) 6250 Å (c) 5000 Å (d) 2500 Å

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Correct Answer: (a) 4000 Å

Explanation:
λ_medium = λ_vac / μ = 5000 / 1.25 = 4000 Å

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

(a) Same direction (b) Opposite direction (c) Zero (d) Alternating

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Correct Answer: (b) Opposite direction

Explanation:
Opposite currents repel

6. A convex lens of focal length 25 cm forms a virtual image at 50 cm. The object distance is:

(a) 50 cm (b) 16.7 cm (c) 33.3 cm (d) 12.5 cm

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Correct Answer: (b) 16.7 cm

Explanation:
1/v - 1/u = 1/f calculation gives u = -16.7 cm

7. The impedance of a series LCR circuit at resonance is:

(a) Zero (b) R (c) X_L - X_C (d) Infinite

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Correct Answer: (b) R

Explanation:
At resonance, Z = R (minimum)

8. The fuel used in fast breeder reactor is:

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

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

Explanation:
Pu-239 and Th-232 are used in breeder reactors

9. If the mass of a body is increased by 100% and velocity is decreased by 50%, the kinetic energy becomes:

(a) Same (b) Half (c) One-fourth (d) Double

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Correct Answer: (a) Same

Explanation:
KE ∝ m v² → m×2, v/2 → same

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