A 15 g turntable is covered with a uniform layer of dry ice that has a mass of 9.0 g. The angular speed of the turntable and dry ice is initially 0.75 rad/s. What is the angular speed of the turntable once all the dry ice has evaporated?

1.2 rad/s

Explanation:

m1 = 15 g, m2 = 9 g, ω1 = 0.75 rad/s

Let the new angular speed is ω2 and the radius of the table be r.

The angular momentum is conserved when no external torque is applied.

I1 ω1 = I2 ω2

(m1 + m2) x r^2 x 0.75 = m1 x r^2 x ω2

(15 + 9) x 0.75 = 15 x ω2

ω2 = 1.2 rad/s