JEE Mains · Physics · STD 11 - System of particles and rotational motion
- JEE Mains 2021
- Hard
- MCQ
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
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Answer & Solution
Correct Answer
(D) \(L _{ A }\) is constant, both in magnitude and direction
Step-by-step Solution
Detailed explanation
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.
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