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Question: Answered & Verified by Expert
A circular disc of moment of inertia $3.5 \mathrm{~kg} \mathrm{~m}^2$ is rotating with angular speed $30 \mathrm{rad} \mathrm{s}^{-1}$ about an axis passing through its centre and perpendicular to its plane. The torque required to stop the disc in 5 seconds is
PhysicsRotational MotionAP EAMCETAP EAMCET 2023 (17 May Shift 2)
Options:
  • A $84 \mathrm{Nm}$
  • B $42 \mathrm{Nm}$
  • C $10.5 \mathrm{Nm}$
  • D $21 \mathrm{Nm}$
Solution:
2330 Upvotes Verified Answer
The correct answer is: $21 \mathrm{Nm}$
Moment of inertia of circular disc, $I=3.5 \mathrm{kgm}^2$ Angular speed, $\omega=30 \mathrm{rad} / \mathrm{s}$
The torque required to stop the disc in 5 seconds
$\tau=\frac{\mathrm{I} \omega}{\mathrm{t}}=\frac{3.5 \times 30}{5}=21 \mathrm{Nm}$

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