Q. On the centre of a frictionless table a small hole is made, through which a weightless string of length $2l$ is inserted. On the two ends of the string two balls of the same mass $m$ are attached. Arrangement is made in such a way that half of the string is on the table top and half is hanging below. The ball on the table top is made to move in a circular path with a constant speed $v$. What is the centripetal acceleration of the moving ball
A) $mvl$
B) $g$
C) Zero
D) $2mvl$
Explanation
(b) [image:4_image150.emf]
Tension $T$ in the string will provide centripetal force
$\Rightarrow \frac{mv^{2}}{l} = T$ …(i)
Also, tension $T$ is provided by the hanging ball of mass $m$,
$\Rightarrow T = mg$ …(ii)
$mg = \frac{mv^{2}}{l} \Rightarrow g = \frac{v^{2}}{l}$
It is the centripetal acceleration of a moving ball
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.