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An energy of 484 J is spent in increasing the speed of a flywheel from 60 rpm to 360 rpm. The moment of inertia of the flywheel is

Asked in Re-NEET 2022 · Rotational energy and released bodies

• (1) 0.07 kg m²
• (2) 0.7 kg m²
• (3) 3.22 kg m²
• (4) 30.8 kg m²

Step-by-step solution

Why the other options are wrong

• (1) comes from is a factor of ten low; with I=0.07 kg m² the same change of speed would take only 1/2(0.07)(140π²)=48 J
• (3) comes from no single slip reproduces 3.22 kg m²; with that value the same change of speed would take 1/2(3.22)(140π²)=2225 J, far more than the 484 J spent
• (4) comes from dividing by the change in angular speed rather than by the change in its square: (2×484)/(10π)=30.8

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