While the turntable is being accelerated, the person suddenly extends her legs. What happens to the turntable?

(a) It suddenly speeds up;

(b) It rotates with constant speed;

(c) Its acceleration decreases;

(d) It suddenly stops rotating.

The moment of inertia of the human body about an axis through its center of mass is important in the application of biomechanics to sports such as diving and gymnastics. We can measure the body€™s moment of inertia in a particular position while a person remains in that position on a horizontal turntable, with the body€™s center of mass on the turntable€™s rotational axis. The turntable with the person on it is then accelerated from rest by a torque that is produced by using a rope wound around a pulley on the shaft of the turntable. From the measured tension in the rope and the angular acceleration, we can calculate the body€™s moment of inertia about an axis through its center of mass.

Overhead view of a female gymnast lying in somersault position atop a turntable