Question

A bob of mass m attached to an inextensible string of length I is suspended from a vertical support. The bob rotates in a horizontal circle with an angular speed `omega` red/s about the vertical. About the point of suspension:
A. angualr momentum changes in direction but not in magnitude,
B. angular momentum changes both in magnitude and direction,
C. angular momentum is conserved,
D. angular momentum changes in magnitude, but not in direction.

Answer 1

Correct Answer - A
Angular momentum of the bob about the point of suspension Fig.
`overset rarr(L) = I omega = (mr^(2)) omega = m (l sin theta)^(2) omega`
`= (ml^(2) sin^(2) theta) omega`
As `m, l, theta and omega` are constants, therefore `overset rarr(L)` is constant in magnitude. However, its direction keeps on changing being perpendicular to `L`, always.