Problem about uniform thin disk

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  • #1
Another
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Why do they only think of kinetic energy of motion?
Why don't they think of both kinetic of motion and kinetic of rolling energy?

So. i think
## L = \frac{1}{2}mv^2 + \frac{1}{2}I \omega^2##
## L = \frac{1}{2}m(r \omega)^2 + \frac{1}{2}(\frac{1}{2}mr^2) \omega^2##
## L = \frac{3}{4} mr^2 \omega^2##
 

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  • #2
kuruman
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Look at the last three equations in the answer. The result will be the same whether you multiply ##mr^2\omega^2## by ##\frac{3}{4}## or ##\frac{1}{2}##. It looks like whoever wrote the solution knew the bottom line and became sloppy.
 
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