Question

A stone attached to one end of a string is whirled in a vertical circle. The tension in the string is maximum when

• A. the string is horizontal
• B. the string is vertical with the stone at highest position
• C. the string is vertical with the stone at the lowest position
• D. the string makes an angle of ${45}^{\circ }$ with the vertical

Answer 1

Answer: (C)

the string is vertical with the stone at the lowest position

$Answer:-$ C

When the stone is at the bottom position forces acting on stone are:

Upward force tension (T), Downward forces are weight (mg) and also $\frac{m{v}^2}{R}$ centrifugal force

So balancing forces we get :

$T=mg+\frac{m{v}^2}{R}$

And minimum tension is obtained at highest point which will be:

$T=mg-$$\frac{m{v}^2}{R}$