Question

A spinning flywheel is dropped onto another flywheel that is initially at rest. After a few seconds the two flywheels are spinning at the same speed. What concept should be used to calculate the final angular velocity?

Answer 1

Use conservation of momentum

I ω = I1 ω1 + I2 ω2 = I1 ω1 initially = I1 ω1 since ω2 = zero

I ω = a constant

(I1 + I2) ω is the final angular momentum

or (I1 + I2) ω = I1 ω1