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If a solid sphere of mass 200g and radius 20cm is rotating with an angular velocity of 5 rad s^-1, its rotational kinetic energy is _____(a) 0.06J(b) 0.04J(c) 0.03J(d) 0.004JThis question was addressed to me in exam.This intriguing question originated from Kinetic Energy in portion Work, Energy and Power of Physics – Class 11

Answer»

Right option is (b) 0.04J

The explanation is: Rotational kinetic ENERGY is given by 0.5*I*Ω^2. I of a solid SPHERE is given by (2/5)*m*r². So, rotational kinetic energy is 0.5*0.4*(200/1000)*(20/100)^2*5^2 = 0.04J.



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