Q: A bob of mass m attached to an inextensible string of length l is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed ω rad/s about the vertical support. About the point of suspension
(a)Angular momentum is conserved
(b)Angular momentum changes in magnitude but not in direction
(c)Angular momentum changes in direction but not in magnitude
(d)Angular momentum changes both in magnitude and direction
Ans: (c)
Sol: As Angular Momentum
$\large \vec{L} = \vec{r} \times \vec{p}$
$\large \vec{L} = \vec{r} \times m\vec{v}$
$\large \vec{L} = m(\vec{r} \times \vec{v})$