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A uniform metallic rod rotates about it...

A uniform metallic rod rotates about its perpendicular bisector with constant angualr speed. If it is heated uniformly to raise its temperature slightly, then

A

Its speed of rotation increases

B

Its speed of rotation decreases

C

Its speed of rotation remains same

D

Its speed increases because its moment of inertia increases

Text Solution

Verified by Experts

The correct Answer is:
B
When the rod is heated, it expands. No external torque is acting on the system so angular momentum should be conserved.

L = Angular momentum = `I omega `= constant
`rArr I_(1) omega_(1) = I_(2) omega_2`
Due to expansion of the rod `I_(2) gt I_(1)`
`rArr (omega_2)/(omega_1) (I_1)/(I_2) lt 1 rArr omega_2 lt omega_1`
So, angular velocity (speed of rotation) decreases.
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