Classical Mechanics (Kibble & Berkshire) · Problem 11.4
Lagrange's equations and conservation principles — T.W.B. Kibble, F.H. Berkshire
Physics — Mechanics · rotating-gas-cloud
Problem
Rotating gas cloud A cloud of interstellar gas of total mass M can move freely in space. Initially the cloud has the form of a uniform sphere of radius a rotating with angular speed Ω about an axis through its centre. Later, the cloud is observed to have changed its form to that of a thin uniform circular disk of radius b which is rotating about an axis through its centre and perpendicular to its plane. Find the angular speed of the disk and the increase in kinetic energy of the cloud.