Question

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 $\omega \,rad/s$ 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 direction and magnitude

Answer 1

Answer: (C)

Angular momentum changes in direction but not in magnitude

Answer 2

$\tau=mg \times l \,\sin \,\theta$ (Direction parallel to plane of rotation of particle)

as $\tau$ is perpendicular to $\vec{L}$, direction of $L$ changes but magnitude remains same