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Rotational kinetic energy
Intermediate
Energy of spinning bodies.
K = ½Iω²A spinning body has K = ½Iω², where I is its moment of inertia. For the same mass, mass farther from the axis stores more energy at the same ω.
A flywheel of I = 2 kg·m² at 100 rad/s: 10 kJ.
Total energy of a rolling body is translation plus rotation.
In more detail
Rotational kinetic energy is ½Iω², where I is the moment of inertia and ω is the angular velocity. It is the energy stored in a spinning object.
Real-world uses
- Flywheels store rotational kinetic energy for buses and hybrid vehicles.
- Turbines store energy in their rotating blades.
- A flywheel stores energy by spinning fast, and the energy depends on its moment of inertia and angular speed.
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Frequently asked questions
Why does moment of inertia matter?
Because a larger moment of inertia stores more energy at the same angular speed.
Is rotational energy part of total kinetic energy?
Yes. A rolling object has both translational and rotational kinetic energy.
Why do flywheels spin so fast?
Kinetic energy grows with the square of angular speed, so high speed stores a lot of energy in a compact, light wheel.
Related topics in Work, Energy & Power
Power of engines and climbers · Escape from a potential well · Work in rotation · Rolling without slipping energy · Work done by gravity on incline · Heat as energy transfer