# Record and turntable, Physics help. I need the solved equations, but cannot get them right for some reason.?

edited

Part A

What is the final angular velocity, ωf, of the two disks?

Express ωf in terms of It, Ir, and ωi.

Part B

Because of friction, rotational kinetic energy is not conserved while the disks' surfaces slip over each other. What is the final rotational kinetic energy, Kf, of the two spinning disks?

Express the final kinetic energy in terms of It, Ir, and the initial kinetic energy Ki of the two-disk system. No angular velocities should appear in your answer.

selected by

A) ωf = ωi * It / (It + Ir)

B) Ki = ½ * It * ωi²

Kf = ½ * (It + Ir) * ωf² = ½ * (It + Ir) * [ωi * It / (It + Ir)]² → some (It + Ir) cancel

Kf = ½ * ωi² * It² / (It + Ir) = ½ * It * ωi² * It / (It + Ir)

Kf = Ki * It / (It + Ir)

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat.

+1 vote