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Originally Posted by threewingedfury
ok cool - I just didnt think people would want to deal with so many questions lol
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I'm no math guy, so the conceptual one is the only one I can answer. . .
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Two uniform circular disks have the same mass and the same thickness are made from different materials. The disk with the smaller rotational inertia is:
a. the one made from the more dense material
b. the one made from the less dense material
c. neither - both are the same
d. the disk with the larger angular velocity
e. the disk with the larger torque
I thought this one was b.
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Correct me if I'm wrong but if they're uniform and they have the same mass and the same thickness, then the material they're made from is a red herring. The answer is C because rotational inertia is determined by the mass and where the mass is concentrated. In other words, if they weren't uniform then one disk could have most of its mass on the inside and the other have most of its mass on the outside, and therefore the smaller rotational inertia would be the disk with more mass on the inside. But if they're uniform then as far as rotation is concerned their physical properties are identical.