A body is dropped from a height of 20 m. Its velocity on reaching ground (g=10) is MCQ with Answer and Explanation

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A body is dropped from a height of 20 m. Its velocity on reaching ground (g=10) is

A. 14.14 m/s

B. 10 m/s

C. 20 m/s

D. 40 m/s

Answer: Option C

Solution (By JKExamLibrary)

v² = 2gh = 2×10×20=400, v=20 m/s.

This question belongs to: Science Physics

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Question #1 Report Error

The speed of sound in air at 0°C is 331 m/s. At 22°C, approximately

A. 350 m/s

B. 331 m/s

C. 343 m/s

D. 360 m/s

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Correct Answer: Option C

Explanation:
v ≈ 331 + 0.6×T(°C) = 331 + 0.6×22 = 331+13.2 = 344.2 m/s, nearest 343 m/s.

This question belongs to: Science Physics

Question #2 Report Error

If the error in the measurement of the momentum of a particle is +100%, what will be the percentage error in the measurement of its kinetic energy?

A. 100%

B. 200%

C. 300%

D. 400%

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Correct Answer: Option C

Explanation:
Kinetic Energy (K) is given by K = p^2 / 2m. If momentum (p) increases by 100%, the new momentum is p' = p + 1.0p = 2p. The new kinetic energy is K' = (2p)^2 / 2m = 4(p^2 / 2m) = 4K. The increase is 4K - K = 3K. Percentage increase = (3K/K) * 100 = 300%.

This question belongs to: Science Physics

Question #3 Report Error

A device that converts light energy into electrical energy is

A. Solar cell

B. Laser

C. Photodiode

D. LED

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Correct Answer: Option A

Explanation:
Solar cell (photovoltaic cell) generates electricity from sunlight.

This question belongs to: Science Physics

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