# physic

posted by
**Mary** on
.

A student on a piano stool rotates freely with an angular speed of 3.07 rev/s. The student holds a 1.38 kg mass in each outstretched arm, 0.759 m from the axis of rotation. The combined moment of inertia of the student and the stool, ignoring the two masses, is 4.72 kg·m2, a value that remains constant.

a. As the student pulls his arms inward, his angular speed increases to 3.54 rev/s. How far are the masses from the axis of rotation at this time, considering the masses to be points?

b. Calculate the initial and final kinetic energy of the system.