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A thin uniform rod of length 2 m, cross-sectional area A and density d is rotated about an axis passing through the centre and perpendicular to its length with angular velocity ω. If the value of ω in terms of its rotational kinetic energy E is √(α E)/(Ad), then the value of α is ______.

Asked in JEE Main 30th Jan 1st Shift 2023 · Rotational energy and released bodies

Answer: 3

Step-by-step solution

The rod's mass is its volume times its density: M=A L d=A(2)d=2Ad.

About a perpendicular axis through the centre: I=(ML²)/(12)=((2Ad)(4))/(12)=(2Ad)/3.

Rotational kinetic energy: E=1/2Iω²=1/2·(2Ad)/3ω²=(Ad ω²)/3.

Rearranging: ω²=(3E)/(Ad).

ω=√(3E)/(Ad), so α=3.

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