Question

A body of mass, $m$, is rotated in a vertical circle of radius, $R$, by means of a light string. If the velocity of body is $\sqrt{5gR}$ at the lowest point of vertical circle, then tension in the string is:

• A. $2mg$
• B. $3mg$
• C. $4mg$
• D. $6mg$

Answer 1

The correct option is D $6mg$

At lowest point, tension acts in upward direction, weight, $mg$, in downward direction.
$T-mg$ provides necessary centripetal force.
$T-mg=\frac{m{\nu }^2}{R}$
$\Rightarrow T=6mg$