Q. In a loop-the-loop, a body starts at a height $h = 2R$. The minimum speed with which the body must be pushed down initially in order that it may be able to complete the vertical circle is
A) $\sqrt{2gR}$
B) $\sqrt{gR}$
C) $\sqrt{3gR}$
D) $2\sqrt{gR}$
Explanation
(b) In going from $C$ to $A$, potential energy lost = potential energy gained in going from $A$ to $B$
For looping the loop, minimum velocity required at $B$ is $\sqrt{gR}.$ This must be the velocity of push down initially from $C$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.