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NEET PHYSICSRotational motionMedium

Question

Three objects, AA (a solid sphere), BB (a thin circular disk) and CC (a circular ring), each have the same mass MM and radius RR. They all spin with the same angular speed about their own symmetry axes. The amount of work (WW) required to bring them to rest, would satisfy the relation:

A

WC>WB>WAW_C > W_B > W_A

B

WA>WB>WCW_A > W_B > W_C

C

WB>WA>WCW_B > W_A > W_C

D

WA>WC>WBW_A > W_C > W_B

Step-by-Step Solution

The work required to bring a rotating object to rest is equal to the change in its kinetic energy of rotation. Since the final kinetic energy is zero, the magnitude of work done is equal to its initial kinetic energy. W=ΔK=12Iω2W = \Delta K = \frac{1}{2} I \omega^2 Given that all objects have the same mass MM, radius RR, and spin with the same angular speed ω\omega, the work done is directly proportional to their moment of inertia II. Moment of inertia of a solid sphere (about its symmetry axis), IA=25MR2=0.4MR2I_A = \frac{2}{5} MR^2 = 0.4 MR^2 Moment of inertia of a thin circular disk (about its symmetry axis), IB=12MR2=0.5MR2I_B = \frac{1}{2} MR^2 = 0.5 MR^2 Moment of inertia of a circular ring (about its symmetry axis), IC=MR2=1.0MR2I_C = MR^2 = 1.0 MR^2 Comparing the moments of inertia, we get IC>IB>IAI_C > I_B > I_A. Therefore, the work required satisfies the relation WC>WB>WAW_C > W_B > W_A.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Rotational motion. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSRotational motionobjectsspherecircularcircularradius

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