JEE Main 2021PhysicsRotational MotionEasyMCQ

JEE Main 2021 — Rotational Motion Question with Solution

JEE Main 2021 (17 Mar Shift 1)

Question

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 ω. The angular momentum of M about point A is LA which lies in the positive z direction and the angular momentum of M about B is LB. The correct statement for this system is:

Choose an option

Show full solutionCorrect option: D
Correct answer
DLA is constant, both in magnitude and direction

Step-by-step explanation

We know, L→=m(r→×v→)

Now with respect to A, we always get direction
of L→ along +ve z-axis and also constant magnitude as mvr. But with respect to B, we get constant magnitude but continuously changing direction.

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About this question

This is a previous-year question from JEE Main 2021, covering the Rotational Motion chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.