(a) What happens to the work done when the displacement of a body is at right angles to the direction of force acting on it? Explain your answer.
(b) A force of $50\ N$ acts on a body and moves it a distance of $4\ m$ on a horizontal surface. Calculate the work done if the direction of force is at an angle of $60^{o}$ to the horizontal surface.

(a). Work done $W=Fs\cos\theta$

If the angle between the direction of the applied force and the displacement is $90^o$, then $\cos90^o=0$

Therefore work done $W=Fs\times 0=0$

Therefore, the work done will be zero if the displacement of a body is at right angles to the direction of force acting on it.

(b).  Here given, applied force $F=50\ N$

Displacement $s=4\ m$

Angle to te horizontal surface $\theta=60^o$

Therefore, work done $W=Fs\cos\theta$

$=50\ N\times 4\ m\times cos60^o$

$=200\times(\frac{1}{2})$

$=100\ J$

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Updated on: 10-Oct-2022

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