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Rotational kinetic energy
Intermediate
Energy stored in spinning.
K = ½Iω²K = ½Iω². Sum of ½mv² of all particles.
A 3 kg·m² flywheel at 50 rad/s stores 3750 J.
Flywheels store energy.
In more detail
Rotational kinetic energy is ½Iω². For a body that both rotates and translates, the total kinetic energy is the sum of translational and rotational energies.
Real-world uses
- Flywheels store energy in rotation for buses and power grids.
- Rolling balls split their kinetic energy between translation and rotation.
- A spinning top, a gyroscope and a flywheel all store kinetic energy in rotation, which can be recovered or released.
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Frequently asked questions
Is rotational energy real energy?
Yes. It can be converted to other forms, such as heat through friction.
Why does a hoop have more rotational energy than a disc?
Because its moment of inertia is larger for the same mass and angular velocity.
How is rotational kinetic energy found?
Use one half times the moment of inertia times the square of the angular velocity.
Related topics in Rotational Motion
Perpendicular axis theorem · Radius of gyration · Newton's second law for rotation · Rolling without slipping · Rolling down an incline · Race of rolling bodies