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A ball rolls without slipping. The radius of gyration of the ball about an axis passing through its centre of mass is K. If radius of the ball be R, then the fraction of total energy associated with its rotational energy will be

Asked in CBSE AIPMT 2003 · Rolling kinematics and energy

Answer: (3) (K²)/(K²+R²)

Step-by-step solution

Given: a ball rolling without slipping, radius of gyration K, radius R, so I=mK² and v=ω R.

Kᵣ=1/2Iω²=1/2mK²(v²)/(R²)=1/2mv²(K²)/(R²)

Kₜ=1/2mv²

Idea: divide the rotational part by the sum, and the common 1/2mv² cancels.

(Kᵣ)/(Kₜ+Kᵣ)=(K²/R²)/(1+K²/R²)

Multiply top and bottom by R²: (K²)/(K²+R²)

Why the other options are wrong

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