A circular disk of moment of inertia Iₐ is rotating in a horizontal plane, its symmetry axis, with a constant angular speed ωₐ. Another disk of moment of inertia Iᵦ is dropped coaxially onto the rotating disk. Initially the second disk has zero angular speed. Eventually both the disks rota

Question

A circular disk of moment of inertia Iₐ is rotating in a horizontal plane, its symmetry axis, with a constant angular speed ωₐ. Another disk of moment of inertia Iᵦ is dropped coaxially onto the rotating disk. Initially the second disk has zero angular speed. Eventually both the disks rotate with a constant angular speed ωf. The energy lost by the initially rotating disk to friction is:

Accepted Answer

1/2 * Iₐ² / (Iₐ + Iᵦ) * ωₐ². The system conserves angular momentum, so the final angular speed ωf is determined by equating the initial and final angular momentum. The energy lost is the difference between the initial rotational kinetic energy and the final rotational kinetic energy. After solving, the energy lost is given by the formula in option A.

Solution

Related NEET Physics questions