Formula
For a mass moving in a straight line:
Joules = ½ × kg × (m/s)²
Rotational energy needs a moment of inertia, which this page does not take. Potential energy is a separate page.
Assumptions
- Mass is kilograms and speed is meters per second.
- The motion is translational, not spinning.
Worked example
2 kg at 3 m/s has 9 J of kinetic energy.
Input definitions
- Mass
- The moving mass in kilograms.
- Speed
- The speed in meters per second.
Limitations
This is a classroom calculation. It is not a laboratory procedure, a wiring plan, or a measured instrument reading.
Questions
Why does speed matter more than mass?
Speed is squared. Doubling speed multiplies the energy by four if the mass stays the same.
Is a joule a newton-meter?
Yes. One joule is one newton applied through one meter.