Question

A circular platform is free to rotate in a horizontal plane about a vertical axis passing through its center. A tortoise is sitting at the edge of the platform. Now, the platform is given an angular velocity ω₀. When the tortoise moves along a chord of the platform with a constant velocity (with respect to the platform), the angular velocity of the platform ω (t) will vary with time t as

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Answer 2

The angular momentum (L) of the system is conserved i.e. L = Iω = constant

When the tortoise walks along a chord, it first moves closer to the centre and then away from the centre. Hence, M.I. first decreases and then increases. As a result, $\omega$ will first increase and then decrease. Also the change in $\omega$ will be non-linear function of time.