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Question
A uniform metallic rod rotates about its perpendicular bisector with constant angular speed. If it is heated uniformly to raise its temperature slightly ______.
Options
its speed of rotation increases.
its speed of rotation decreases.
its speed of rotation remains same.
its speed increases because its moment of inertia increases.
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Solution
A uniform metallic rod rotates about its perpendicular bisector with constant angular speed. If it is heated uniformly to raise its temperature slightly its speed of rotation decreases.
Explanation:
As the rod is heated, it expands. No external torque is acting on the system so angular momentum should be conserved.
L = Angular momentum = Iω = constant
⇒ I1ω1 = I2ω2
Due to the expansion of the rod I2 > I1
⇒ `ω_2/ω_1 = I_1/I_2 < 1`
⇒ `ω_2 < ω_1`
So, angular velocity (speed of rotation) decreases.
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