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A solid sphere is in rolling motion. In rolling motion a body possesses translational kinetic energy (Kₜ) as well as rotational kinetic energy (Kᵣ) simultaneously. The ratio Kₜ:(Kₜ+Kᵣ) for the sphere is

Asked in NEET 2018 · Rolling kinematics and energy

• (1) 7 : 10
• (2) 5 : 7
• (3) 10 : 7
• (4) 2 : 5

Step-by-step solution

Why the other options are wrong

• (1) comes from reading 7/(10) off the total energy 7/(10)mv²; that number compares the total with mv², not the translational part with the total
• (3) comes from the reciprocal of option (a). A part cannot exceed the whole, so any ratio greater than 1 is out
• (4) comes from this is (Kᵣ)/(Kₜ)=((1/5)mv²)/((1/2)mv²), the rotational part compared with the translational part

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