Q24 of 48 Page 45

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) When force is applied to raise the body then the angle

between force and displacement is 0°.


∴ Work done =Fscosθ =Fscos0=Fs


sign of work done is positive.


(b)As gravitational force acts in downward direction then the


angle between force and displacement is 180°.


∴ work done =Fscosθ =Fscos180°=-Fs.


sign of work done is negative.


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