$A$ body is being raised to height $h$ from the surface of the Earth. What is the sign of work done by $(a)$ applied force and $(b)$ gravitational force?
(N/A) Force is applied on the body to lift it in the upward direction,and the displacement of the body is also in the upward direction.
Since the angle between the applied force and displacement is $0^{\circ}$,the work done by the applied force is $W = F d \cos 0^{\circ} = F d$,which is positive.
$(b)$ The gravitational force acts in the downward direction,while the displacement is in the upward direction.
Since the angle between the gravitational force and displacement is $180^{\circ}$,the work done by the gravitational force is $W = F d \cos 180^{\circ} = -F d$,which is negative.
Since the angle between the applied force and displacement is $0^{\circ}$,the work done by the applied force is $W = F d \cos 0^{\circ} = F d$,which is positive.
$(b)$ The gravitational force acts in the downward direction,while the displacement is in the upward direction.
Since the angle between the gravitational force and displacement is $180^{\circ}$,the work done by the gravitational force is $W = F d \cos 180^{\circ} = -F d$,which is negative.
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