Kinetic energy of rotation

Classical Mechanics Level 2

A ring of radius 0.5 m 0.5\text{ m} and mass 10 kg 10\text{ kg} is rotating about its diameter with an angular velocity of 20 rad/s . 20\text{ rad/s}. Its kinetic energy is __________ . \text{\_\_\_\_\_\_\_\_\_\_}.

500 J 10 J 100 J 250 J

Rohit Gupta by Rohit Gupta , 34, India

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1 solution

Gaurav Agarwal
Oct 28, 2016

K.E. = 1/2Iw^2 =1/2× 1/2 mr^2 × 20^2 Putting associated value K.E.= 250 joules

2 Helpful 0 Interesting 0 Brilliant 1 Confused

It is a ring and not a disc. Hence moment of inertia of a body as entered is incorrect. I think the answer has to be 500J.

Sarthak Shiv - 3 years, 7 months ago

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I agree a ring's moment of inertia is m r^2 not 1/2 m*r^2 so the answer is suppose to be 500J.

Ofek Tevet - 1 year, 7 months ago

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