JEE Main 2022 · 30 Jul · Shift 2 · Physics Q28

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A fly wheel of mass 10 kg and radius 50 cm is rotating at a rate of 360 rpm. Assuming mass to be concentrated at the rim, the constant retarding torque required to stop the rotation of wheel in 6 rotations will be $x\pi$ N m. The value of $x$ is _______

Your answer

Answer and worked solution

Official answer: 15

Rotation. $\omega=12\pi$ rad/s, $\theta=12\pi$ rad, $I=10\times0.25=2.5$ kg m².

Torque $\dfrac{I\omega^2}{2\theta}=\dfrac{2.5\times144\pi^2}{24\pi}=15\pi$ N m.

Answer: 15

Topics:Torque and rotational dynamics Moment of inertia

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JEE Main 2022 · 30 Jul · Shift 2, Physics question 28