Kinetic energy is the energy of a moving object, proportional to its mass and the square of its velocity. The unit is the joule (J).
Enter the mass (kg) and velocity (m/s) to instantly get the kinetic energy. A key point: doubling the speed quadruples the kinetic energy.
For example, a 10 kg object moving at 5 m/s has a kinetic energy of 125 J.
Kinetic energy is the energy an object possesses because it is moving. It depends on mass and on the square of speed, so doubling the speed quadruples the energy — which is why stopping distances grow so quickly with velocity.
Enter the mass and velocity to calculate the kinetic energy in joules.
Kinetic energy grows with the square of speed, so doubling velocity quadruples it: a 1,000 kg car at 10 m/s carries 50 kJ, and at 20 m/s carries 200 kJ. That is why stopping distance rises so steeply with speed — four times the braking work is needed for twice the velocity.
KE = ½ × m × v²Energy equals force times distance, and the distance needed to reach a speed grows with the speed itself, so the work done — and therefore the energy — scales with v². Doubling speed quadruples kinetic energy.
A car at 60 mph carries four times the kinetic energy it has at 30 mph, so it needs about four times the braking distance. This is the physics behind speed limits in built-up areas.
The formula is one half mass times speed squared, and squaring 2 gives 4. That is why speed limits have such a large effect on crash severity and on fuel consumption at motorway speeds.
The work done on an object equals its change in kinetic energy. Pushing a 500 kg cart from rest to 4 m/s takes 4,000 J, the same as applying 400 N over 10 m without friction.
2026-10-19