Question

A singer, during his performance, stands on the edge of a circular turntable and begins to walk along its edge with a speed of $5\text{ m s}^{-1}$ relative to the ground. The turntable is mounted on a frictionless vertical axle. Its radius $R = 3\text{ m}$ and its moment of inertia about the axle is $150\text{ kg m}^2$. It is initially at rest. If the mass of the singer is $75\text{ kg}$, the time taken by the man to complete one full revolution relative to the ground is:

• A. $12.57\text{ s}$
• B. $20.5\text{ s}$
• C. $6.28\text{ s}$
• D. $8.56\text{ s}$

Hint:

Pay close attention to the frame of reference specified in the question! Since the speed and the final revolution are both given relative to the ground, the calculation simplifies directly to $t = \frac{2\pi R}{v}$, making conservation of angular momentum extra information that confirms the system's physical behavior.

Answer 1

The Correct Option is A