- #1
Titan97
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Homework Statement
A rod attached to a ceiling at one end and a disc on the other end is performing SHM. In case (1) the disc cannot rotate. In case (2) the disc can rotate about its centre. Compare the restoring torque and angular frequency in both cases.
Homework Equations
$$T=2\pi\sqrt{\frac{I}{MgL}}$$
The Attempt at a Solution
I think the restoring torques are same. But my friend says there will be hinge forces that will affect the restoring torque in case (2) because of rotation of disc which causes centripetal force on disc.
In the second question, again we got different answers. Using the formula specified above, the frequency will be different because of an additional moment of inertia in case (2). My friend told that even if the disc is not rotating in case (1), it's moment of inertia is still ##\frac{Mr^2}{2}##. So he says the the frequency is same.
I am confused now. Is moment of inertia only for rotating objects?
(Both my answers match with the given solution)