Question

A particle of mass $200g$ is moving in a circle of radius $2m$. The particle is just "looping the loop". The speed of the particle and the tension in the string at highest point of the circular path are ($g=10m/s^2$)

• A. $4m{s}^{-1},5N$
• B. $4.47m{s}^{-1},0$
• C. $2.47m{s}^{-1},0$
• D. $1m{s}^{-1},0$

Answer 1

The correct option is B $4.47m{s}^{-1},0$

The body will revolve in the circle if the string does not sag.

$T_H\ge 0$

or, $T_H+mg=\frac{m{u}^2}{r}$

For minimum, $T_H=0$

$\therefore u=\sqrt{rg}=4.47m{s}^{-1}$