Question

A body is tied at the end of a string of length " and rotated in a vertical circle, The suring is just taut when the body is at highest point. Velocity of the body when the string is in horizontal position is

• A. 3$\sqrt{gr}$
• B. $\sqrt{gr}$
• C. $\sqrt{5gr}$
• D. $\sqrt{3gr}$

Answer 1

The correct option is C $\sqrt{5gr}$

$\begin{array}{c}T+mg=\frac{m{u}^2}{R}\\ \Rightarrow T=0\\ u^2=kg\\ mg\left(2R\right)=\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^2\\ \Rightarrow 4gR=v^2-u^2\\ \Rightarrow v=\sqrt{5gR}\\ Hence,\\ optionCiscorrectanswer.\end{array}$