Q. One end of a string of length $l$ is connected to a particle of mass $m$ and the other to a small peg on a smooth horizontal table. If the particle moves in a circle with speed $v$, the net force on the particle (directed towards the centre) is
A) $T$
B) $T - \frac{mv^{2}}{l}$
C) $T + \frac{mv^{2}}{l}$
D) Zero
Explanation
(a) When particle moves in a circle, then the resultant force must act towards the centre and its magnitude $F$ must satisfy, $F = \frac{mv^{2}}{l}$
This resultant force is directed towards the centre and it is called centripetal force. This force originates from the tension $T$
Hence, $F = \frac{mv^{2}}{l} = T$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.