A constant torque acting on a uniform circular wheel changes its angular momentum from $A_0$ to $4A_0$ in $4$ second. the magnitude of this torque is:

A conical pendulum consists of a simple pendulum moving in a horizontal circle as shown. $C$ is the pivot, $O$ the centre of the circle in which the pendulum bob moves and $\omega$ the constant angular velocity of the bob. If $\overrightarrow{L}$ is the angular momentum about point $C$, then

A conical pendulum consists of a simple pendulum moving in a horizontal circle as shown. $C$ is the pivot, $O$ the centre of the circle in which the pendulum bob moves and $\omega$ the constant angular velocity of the bob.