A company advertises a flywheel whose thin rim

PHYSICS · Multi-part · Fermi University Physics · Mechanics & Dynamical Systems · Earth, Climate & Energy Physics · Rotation, rigid bodies and accelerated frames

Energy from Physics, Ch Storing energy: cells, rotors, air, heat and hydrogen

Problem

A company advertises a flywheel whose thin rim, made of carbon fibre of tensile strength

2\,\mathrm{GPa}

and density

1600\,\mathrm{kg\,m^{-3}}

, stores

2\,\mathrm{MJ}

per kilogram of rim. ((a)) Find the largest energy per kilogram a thin rim of this material can hold before it fails, and the factor by which the claim exceeds it. ((b)) Find the rim speed the claim would need, and the hoop stress that speed would put in the rim.

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