A uniform disc is rotating at a constant speed in a vertical plane about a fixed horizontal axis passing through the centre of the disc. A piece of the disc from its rim detaches itself from the disc at the instant when it is at a horizontal level with the centre of the disc and moving upward. Then about the fixed axis, the angular speed of the remaining disc is

Question

A uniform disc is rotating at a constant speed in a vertical plane about a fixed horizontal axis passing through the centre of the disc. A piece of the disc from its rim detaches itself from the disc at the instant when it is at a horizontal level with the centre of the disc and moving upward. Then about the fixed axis, the angular speed of the remaining disc is (A) remains unchanged (B) decreases (C) increases (D) initially increases and later decreases

Tardigrade Admin · Accepted Answer

<img class="img-fluid question-image" alt="Solution" src="https://cdn.tardigrade.in/q/nta/p-en8faih9uzin.png" /> Since the broken away piece of mass m (say) has the same linear speed as it had before detaching from the disc, the angular speed of the remaining disc will remain unchanged.