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A uniform metallic rod rotates about its...

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

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
Rod will be expanded by heating it. Here, there is no external torque on system hence, its angular momentum is conserved.
`:.` In `L=1omega`, L is constant
`:.I_(1)omega_(1)=I_(2)omega_(2)` . .. (1)
Now, due to expansion of rod, its moment of inertia increases.
`:.I_(2)gtI_(1):.(I_(2))/(I_(1))gt1`
From equation (1),
`(omega_(1))/(omega_(2))=(I_(2))/(I_(1))`

`:.(omega_(1))/(omega_(2))gt1`
`:.omega_(2)ltomega_(1)`
Hence, angular speed of rotation decreases.
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