Q. A body slides down a frictionless track which ends in a circular loop of diameter $D$. Then the minimum height $h$ of the body in terms of $D$ so that it may just complete the loop, is
A) $h = \frac{5}{2}D$
B) $h = \frac{3}{2}D$
C) $h = \frac{5}{4}D$
D) $h = 2D$
Explanation
(c) For looping the loop, the velocity at the lowest point of loop should be
$v = \sqrt{5gr} = \sqrt{5gD/2} = \sqrt{2gh}$ or $h = 5\ D/4$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.