Q.
A mass $M$ hangs on a massless rod of length $l$ which rotates at a constant angular frequency. The mass $M$ moves with steady speed in a circular path of constant radius.
Assume that the system is in steady circular motion with constant angular velocity $\omega$. The angular momentum of $M$ about point $A$ is $L _{ A }$ which lies in the positive $z$ direction and the angular momentum of $M$ about $B$ is $L _{ B }$. The correct statement for this system is :

Solution: