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प्रश्न
No work is done by a man moving on a horizontal road while carrying a box on his head. Explain.
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उत्तर
The displacement of the man and box is along the horizontal direction. Thus, the angle between the displacement and the force of gravity is 900;
Thus, W = Fd cos 900 = 0
Hence, no work is done against gravity in this case; however some work is done against friction.
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