The energy of a moving object
Kinetic energy is the energy something has because it is moving. Bring it to a stop and that energy has to go somewhere — into brakes as heat, into crumpling metal in a crash, or into the work a moving tool performs. Understanding it explains everything from road-safety physics to how a wind turbine captures energy from moving air.
How to use the calculator
Enter the object's mass in kilograms and its velocity in metres per second. The calculator returns the kinetic energy in joules and kilojoules.
The formula and why speed dominates
KE = ½ × m × v². The crucial detail is that velocity is squared, so speed matters far more than mass. Double the speed and the kinetic energy quadruples. A 1,000 kg car at 100 km/h (27.8 m/s) carries about 385 kJ of energy; the same car at 120 km/h carries far more, because of that squared term.
Why this matters for road safety
The squared relationship is exactly why speed limits are set where they are. A modest increase in speed causes a large increase in both the energy that must be dissipated in a crash and the distance needed to stop. This is not a linear trade-off — going 20% faster does not make a collision 20% worse, it makes it far worse. The same physics governs falling objects, sports impacts, and the design of safety barriers.