Physics MCQ Practice 9 — Science Foundation Course for Class 11 & 12

1. A train is moving at 90 km/h. It is brought to rest in 10 seconds. The retardation is:

(a) 2.5 m/s² (b) 5 m/s² (c) 9 m/s² (d) 25 m/s²

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Correct Answer: (a) 2.5 m/s²

Explanation:
u = 25 m/s, v = 0, t = 10 s → a = (0-25)/10 = -2.5 m/s²

2. The weight of a body on the Moon is 1/6th of its weight on Earth. The mass on Moon is:

(a) 1/6th (b) Same (c) 6 times (d) Zero

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Correct Answer: (b) Same

Explanation:
Mass is invariant. Weight changes with g.

3. Three resistors 2 Ω, 3 Ω and 6 Ω are connected in parallel. Equivalent resistance is:

(a) 11 Ω (b) 1 Ω (c) 2 Ω (d) 6 Ω

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Correct Answer: (b) 1 Ω

Explanation:
1/R = 1/2 + 1/3 + 1/6 = 1 → R = 1 Ω

4. The fundamental frequency of an open pipe is 300 Hz. The frequency of second overtone is:

(a) 300 Hz (b) 600 Hz (c) 900 Hz (d) 1200 Hz

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Correct Answer: (c) 900 Hz

Explanation:
Second overtone (3rd harmonic) = 3 × 300 = 900 Hz

5. The direction of magnetic field due to current in a straight wire is given by:

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

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Correct Answer: (b) Right hand thumb rule

Explanation:
Right hand thumb rule for straight conductor

6. A concave mirror has focal length 20 cm. For an object at 30 cm, image distance is:

(a) 60 cm (b) -60 cm (c) 12 cm (d) -12 cm

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Correct Answer: (b) -60 cm

Explanation:
1/v + 1/u = 1/f → 1/v = 1/(-20) - 1/(-30) = -1/60 → v = -60 cm

7. In a transformer, core is laminated to reduce:

(a) Eddy current loss (b) Hysteresis loss (c) Copper loss (d) All losses

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Correct Answer: (a) Eddy current loss

Explanation:
Lamination reduces eddy currents

8. The energy released in nuclear fission is due to:

(a) Mass defect (b) Binding energy (c) Both (d) None

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Correct Answer: (c) Both

Explanation:
Mass is converted to energy as per E=mc² due to binding energy difference

9. If the velocity of a body is doubled, its kinetic energy becomes:

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

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Correct Answer: (c) Four times

Explanation:
KE ∝ v ² → velocity doubled → KE becomes 4 times

10. The physical quantity having unit volt per metre is:

(a) Electric field (b) Electric potential (c) Force (d) Magnetic field

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Correct Answer: (a) Electric field

Explanation:
E = V/d → unit V/m