Question

A straight rod of negligible mass is mounted on a frictionless pivot and masses 2.5 kg and 1 kg are suspended at distances 40 cm and 100 cm respectively from the pivot as shown. The rod is held at an angle $\theta$ with the horizontal and released.

• A. The rod executes periodic motion about horizontal position after the release.
• B. The rod remains stationary after the release
• C. The rod comes to rest in vertical position with 2.5 kg mass at the lowest point.
• D. The rod executes periodic motion about vertical position after the release.

Answer 1

The correct option is B

The rod remains stationary after the release

Torque about hinge is

$\left(2.5\right)g(4.5\times {10}^{-2})cos\theta -\left(1\right)g(100\times {10}^{-2})cos\theta =0$

So rod remains stationary after the release.