Question:
A ring and a disc of different masses are rotating with the same kinetic energy. If we apply a retarding torque $\tau$ on the ring, it stops after completing n revolutions in all. If same torque is applied to the disc, how many revolutions would it complete in all before stopping
A ring and a disc of different masses are rotating with the same kinetic energy. If we apply a retarding torque $\tau$ on the ring, it stops after completing n revolutions in all. If same torque is applied to the disc, how many revolutions would it complete in all before stopping
Updated On: Jul 12, 2022
- 4 n
- 2n
- n
- $\frac{n}{2}$
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The Correct Option is C
Solution and Explanation
Because kinetic energy $K_R$ and retarding torque x are same, therefore in accordance with the relation, less in kinetic energy = work done by torque
$=\tau.\theta$
$=\tau.2 \pi n$
So, both ring and disc stop after completing equal number of revolutions n.
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Concepts Used:
System of Particles and Rotational Motion
- The system of particles refers to the extended body which is considered a rigid body most of the time for simple or easy understanding. A rigid body is a body with a perfectly definite and unchangeable shape.
- The distance between the pair of particles in such a body does not replace or alter. Rotational motion can be described as the motion of a rigid body originates in such a manner that all of its particles move in a circle about an axis with a common angular velocity.
- The few common examples of rotational motion are the motion of the blade of a windmill and periodic motion.