Kinetic Energy formula
KE = 12 m v²
| Symbol | Quantity | SI unit | Meaning |
|---|---|---|---|
| KE | Kinetic energy | J | Translational kinetic energy |
| m | Mass | kg | Mass of the moving body |
| v | Speed | m/s | Speed |
What is Kinetic Energy?
Kinetic Energy: The energy of motion of a body equals one half its mass times the square of its speed.
Kinetic energy is the work needed to accelerate a body from rest to speed v. Because it grows with the square of speed, doubling speed quadruples the energy. That is why braking distances and crash severity rise so steeply with speed.
In kinetic theory, the average translational kinetic energy of a gas molecule is (3/2)kBT. This is the link between temperature, molecular speed and diffusion rates (see Graham's law).
How to use this calculator
- Choose the quantity you want to find in the Calculate menu. It is highlighted as the result field.
- Enter the known values. Scientific notation such as
1.6e-11is accepted. - Select a unit for each value. Units are converted to SI automatically.
- The answer updates as you type. Open Show calculation steps to see the working, or use Copy result to share a link with your inputs.
Worked example
A 1500 kg car travels at 90 km/h.
- v = 90 / 3.6 = 25 m/s.
- KE = ½ × 1500 × 25² = 468 750 J ≈ 469 kJ.
Frequently asked questions
Can kinetic energy be negative?
No. Mass is positive and v² is never negative, so KE ≥ 0.
How is kinetic energy related to momentum?
KE = p²/(2m), where p = mv. The calculator shows the momentum as a derived result.