Question

A thin horizontal circular disc is rotating about a vertical axis passing through its centre. An insect is at rest at a point near the rim of the disc. The insect now moves along a diameter of the disc to reach its other end. During the journey fo the insect, the angular speed of the disc.

• A. remains unchanged
• B. continuously decreases
• C. continuously increases
• D. first increases and then decreases

Answer 1

The correct option is D first increases and then decreases


From angular momentum conservation about vertical axis passing through centre: When insect is coming from circumference to center, moment of inertia decreases and when insect is going from centre to circumference, moment of inertia increases. So angular velocity first increases and then decreases.