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weesiang_loke
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Homework Statement
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?
Homework Equations
Initial rotational kinetic energy = 0.5*I*w2
I = 0.5*M*R2
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.