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A body is being raised to height h from ...

A body is being raised to height h from the surface of earth. What is the sign of work done by (a) applied force and (b) gravitational force ?

Text Solution

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(a) Force is applied on the body to lift it in upward direction and displacement of the body is also in upward direction .
` :. ` Work done by the applied force,
`W = Fd cos theta = Fd cos 0^(@) = ` Fs = positive
(b) The gravitational force acts in downward direction and displacement is in upward direction .
` :.` Work done by the gravitational force
`W = Fd cos 180^(@) = - Fd = ` negative
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