Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

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 :
image

JEE MainJEE Main 2021System of Particles and Rotational Motion

Solution:

We know, $\overrightarrow{ L }= m (\overrightarrow{ r } \times \overrightarrow{ v })$
Now with respect to $A$, we always get direction of $\overrightarrow{ L }$ along +ve z-axis and also constant magnitude as mvr. But with respect to $B$, we get constant magnitude but continuously changing direction.