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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.
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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