Q. A body just being revolved in a vertical circle of radius $R$ with a uniform speed. The string breaks when the body is at the highest point. The horizontal distance covered by the body after the string breaks is
A) $2\ R$
B) $R$
C) $R\sqrt{2}$
D) $4\ R$
Explanation
(a) As the body just completes the circular path, hence critical speed at the highest point.
$v_{H} = \sqrt{gR}$
which is totally horizontal.
As the string breaks at the highest point, hence form here onwards the body will follow parabolic path. Time taken by the body to reach the ground
$t = \sqrt{\frac{2h}{g}} = \sqrt{\frac{2 \times 2R}{g}}$
Hence, horizontal distance covered by the body
$= v_{H} \times t$
$= \sqrt{gR} \times \sqrt{\frac{4R}{g}} = 2R$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.