Question

A force $F$ acts on a body and displaces it by a distance $S$ in a direction at an angle $\theta$ with the direction of force. In order to get zero work, the angle $\theta$ between the force and the displacement will be equal to :

• A. ${30}^0$
• B. ${45}^0$
• C. ${60}^0$
• D. ${90}^0$

Answer 1

The correct option is D ${90}^0$

Work done, $W=FScos\theta$

So, for zero work, $FScos\theta =0$

Now, $F$ and $S$ are both not equal to zero.

$\therefore$ $cos\theta =0$

or, $cos\theta =cos{90}^0$

or, $\theta ={90}^0$