In which of the following scenarios is the work done physically zero?
A. All of the above.
B. A person carrying a heavy load on his head and walking on a horizontal road.
C. A satellite moving in a circular orbit around the Earth.
D. A person pushing a heavy wall that does not move.
Answer: Option A
Solution (By JKSSB Mock Tests)
Work (W) = F × d × cos(θ). In scenario A, displacement (d) is zero. In scenario B, the applied force (upward) is perpendicular to the displacement (horizontal), so cos(90°) = 0. In scenario C, the centripetal force (gravity) is perpendicular to the satellite's instantaneous direction of motion, so work done is zero. All cases yield zero work.
Explanation:
Pitch is subjective perception of frequency. Higher frequency higher pitch. Amplitude determines loudness. Speed and wavelength related by v = fλ, but pitch is frequency-based. Human ear 20 Hz-20 kHz.
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