A stone of mass 1 kg is tied with a string and it is whirled in a vertical circle of radius 1m. If tension at the highest point is 14N, then velocity at lowest point will be:

The correct option is:C: 6 m/s

Mass of the stone, $m=1kg$

Radius, $r=1m$

Tension, $T=14N$

Let $v_1$ is velocityat the top point and $v_2$ is at the bottom point.

The tension at the top pointis:

$T=\frac{m{v}_1^2}{r}+mg$

$14=\frac{\left(1\right)v_1^2}{1}+g⟹14=v_1^2+10$

$v_1^2=4⟹v_1=2$

So, total kinetic energy atthe bottom is:

$\frac{1}{2}m{v}_2^2={\left(mgh\right)}_{bottom}+\frac{1}{2}m{v}_1^2$

$\frac{1}{2}m{v}_2^2=20+2$

$v_2^2=44⟹v=\sqrt{44}=6.63{ms}^{-1}$