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A body is being raised to a height h fro...

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

A

Positive, Positive

B

Positive, Negative

C

Negative, Positive

D

Negative, Negative

Text Solution

Verified by Experts

The correct Answer is:
B
Work done, `W=vecF.vecd=Fd cos theta`
where `theta` is the angle between the force `vecF` and displacement `vecd`
(i) As the body moves along the direction of applied force.
` therefore theta =0^@`, `W = Fd cos theta= Fd`. It is positive.
(ii) As the body moves in a direction opposite to the gravitational force which acts vertically downwards.
`therefore theta=180^@`, `W= Fd cos180^@ =-Fd`.
It is negative.
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