Question

The tension in the string of a simple pendulum is always perpendicular to displacement. So, work done by the tension is

• A. Zero
• B. Positive
• C. Negative
• D. Unity

Answer 1

The correct option is A

Zero

Finding the work done

We know that work done,$W=FS\cos \theta$

where F = force acted, S = displacement, and $\theta$ = gradient between the direction of force and displacement of the body.

Since, the string of a simple pendulum is always perpendicular to displacement,

So, as $\theta ={90}^{\circ }thenCos90=0$

$$\begin{gathered} \therefore W=FS\times 0 \\ W=0 \end{gathered}$$

Thus, work done by the tension is zero.

Hence, option (a) is correct.