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NEET PHYSICSRotational motionEasy

Question

Ratio of total kinetic energy and rotational kinetic energy in the motion of a disc is:

A

1:11:1

B

2:72:7

C

1:21:2

D

3:13:1

Step-by-Step Solution

In pure rolling motion of a disc, the total kinetic energy (KtotalK_{total}) is the sum of its translational kinetic energy (KtK_t) and rotational kinetic energy (KrK_r). Kt=12mv2K_t = \frac{1}{2}mv^2 Kr=12Iω2K_r = \frac{1}{2}I\omega^2 For a disc, the moment of inertia about its central axis is I=12mR2I = \frac{1}{2}mR^2. Also, v=Rωv = R\omega for pure rolling. So, Kr=12(12mR2)(vR)2=14mv2K_r = \frac{1}{2} \left(\frac{1}{2}mR^2\right) \left(\frac{v}{R}\right)^2 = \frac{1}{4}mv^2 Ktotal=Kt+Kr=12mv2+14mv2=34mv2K_{total} = K_t + K_r = \frac{1}{2}mv^2 + \frac{1}{4}mv^2 = \frac{3}{4}mv^2 The ratio of total kinetic energy to rotational kinetic energy is: KtotalKr=34mv214mv2=31=3:1\frac{K_{total}}{K_r} = \frac{\frac{3}{4}mv^2}{\frac{1}{4}mv^2} = \frac{3}{1} = 3:1

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 motionkineticenergyrotationalkineticenergy

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