Question

A stone of mass $m$ tied to a string of length $l$ is rotating along a circular path with constant speed $v$. What will be the torque on the stone?

Answer 1

Step 1: Given:

Stone mass = m

string of length = l

velocity = V

Step 2: Formula

Torque is given by$$\begin{gathered} \tau =r\times F \\ =r\times \frac{m{v}^2}{r} \end{gathered}$$

$a$ is acceleration.

r is the axle radius.

v is the speed.

m is the mass of stone.

Step 3: Solution

As the direction of centripetal force and position vector is directed toward center

$$\begin{gathered} T=r\times F \\ =rF\sin \theta \\ here\theta =0^o \\ ThereforeT=0 \end{gathered}$$

The torque will be zero.