1.

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, PositiveB. Positive, NegativeC. Negative, PositiveD. Negative, Negative

Answer» Correct Answer - 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.


Discussion

No Comment Found

Related InterviewSolutions