Question

A small ball of mass $m$ is attached with a light rigid rod of length $l$ and hinged at one of its ends such that it can rotate in vertical plane. Minimum speed $v$ that should be given to the ball at lowest point to complete the vertical circular path is

• A. $\sqrt{7gl}$
• B. $\sqrt{5gl}$
• C. $\sqrt{3gl}$
• D. $\sqrt{4gl}$

Answer 1

The correct option is D $\sqrt{4gl}$

Answer (2)


Using conservation of mechanical energy
$\frac{1}{2}m{v}^2+0=2mgl+0$
$v=\sqrt{4gl}$
Hence, $v_{\text{min}}=\sqrt{4gl}$