1. The problem statement, all variables and given/known data A horizontal thin disc of mass M and radius R rotates about its horizontal axis through its centre with angular speed w. If a chip of mass m breaks off at the edge of the disc, what is the final angular speed of the disc? 2. Relevant equations Initial rotational kinetic energy = 0.5*I*w2 I = 0.5*M*R2 3. The attempt at a solution I assume that the chip broke off can be considered as some point mass. So the new moment of inertia of the thin disc, Inew = 0.5*M*R2 - m*R2. so based on the conservation of kinetic energy: 0.5*I*w2 = 0.5*Inew*wnew2 + o.5*m*(R*w)2 then I substituted in the new moment of inertia and simplified. what i get for wnew is the same as w. That means the speed is unaffected. I am not sure whether this is the correct way to do it? and if so why the speed is not affected by the process? Thanks for any help give.