Question

A simple pendulum of length $L$ swings in a vertical plane. The tension of the string when it makes an angle $\theta$ with the vertical and the bob of mass m moves with a speed $v$ is ($g$ is the gravitational acceleration

• A. $mv^2/L$
• B. $mg\, cos$ $\theta$ + $mv^2/L$
• C. $mg\, cos$ $\theta$ - $mv^2/L$
• D. $mg \,cos$ $\theta$

Answer 1

Answer: (B)

mg\, cos$$\theta + $mv^2/L$

Answer 2

The situation is given below

For motion along a vertical circular track, the required centripetal force is along the radius and towards the centre of the circle is given by
$T-m g \cos \theta =\frac{m v^{2}}{L}$
$\Rightarrow T =\frac{m v^{2}}{L}+m g \cos \theta$