JEE Main 2017 — Rotational Motion Question with Solution
From: JEE Main 2017 (Offline)
Question
A slender uniform rod of mass M and length is pivoted at one end so that it
can rotate in a vertical plane (see figure). There is negligible friction at the
pivot. The free end is held vertically above the pivot and then released. The
angular acceleration of the rod when it makes an angle with the vertical is
This question includes a diagram. The text above accompanies the figure.
Choose an option
Show full solutionCorrect option: B
Correct answer
B
Step-by-step explanation
Forces acting on the rod are shown below.
Torque about pivot point O due to force Nx and Ny are zero.
Mgcos is passing through O, so torque will be zero due to this force.
So torque about the point O is
We know,
Moment of inertia of rod about point O, =
Torque about pivot point O due to force Nx and Ny are zero.
Mgcos is passing through O, so torque will be zero due to this force.
So torque about the point O is
We know,
Moment of inertia of rod about point O, =
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This is a previous-year question from JEE Main 2017, 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.