Question

A particle of mass m is tied to a light string of length l and rotated along a vertical circular path. What should be the minimum speed at a highest point of its path so that the string does not become slack at any position?

• A. $\sqrt{2gl}$
• B. $\sqrt{gl}$
• C. zero
• D. $\sqrt{gl/2}$

Answer 1

The correct option is B $\sqrt{gl}$

For $v_h$ to be minimum, $T_h=0$; where $v_h$ and $T_h$ are velocity and Tension at highest point.
or $v_h=\sqrt{gl}$