A solid disc of radius $ 20 \mathrm{~cm} $ and mass $ 10 \mathrm{~kg} $ is rotating with an angular velocity of $ 600 \mathrm{rpm} $, about an axis normal to its circular plane and passing through its centre of mass. The retarding torque required to bring the disc at rest in $ 10 \mathrm{~s} $ is _____

Question

A solid disc of radius $ 20 \mathrm{~cm} $ and mass $ 10 \mathrm{~kg} $ is rotating with an angular velocity of $ 600 \mathrm{rpm} $, about an axis normal to its circular plane and passing through its centre of mass. The retarding torque required to bring the disc at rest in $ 10 \mathrm{~s} $ is _____, $4 \pi \times 10^{-2}$, $2 \pi$, $4 \pi \times 10^{-1}$, $2 \pi \times 10^{-2}$

MARKS App · Accepted Answer

τ = Δ L Δ t = I ω f - ω i Δ t τ = m R 2 2 × [ 0 - ω ] Δ t = 10 × 20 × 10 - 2 2 2 × 600 × π 30 × 10 = 0 . 4 π = 4 π × 10 - 2

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