Calculate kinetic energy, mass, or velocity from the other two using KE = ½mv², with energy unit conversions and equivalent drop-height context.
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Kinetic Energy
9 J
Energy (J)
9.00
Mass (kg)
2.000
Velocity (m/s)
3.000
Equivalent drop height: 0.46 m
Also in Physics
Science — Physics
Kinetic energy is the energy an object possesses due to its motion. The equation KE = ½mv² relates kinetic energy to mass and velocity — one of the most fundamental results in classical mechanics.
KE = ½mv² where m is mass in kilograms and v is speed in metres per second. Kinetic energy is measured in joules (J). The equation can be rearranged to find mass (m = 2KE ÷ v²) or velocity (v = √(2KE ÷ m)).
Kinetic energy scales with the square of velocity: doubling speed quadruples kinetic energy. This is why vehicle collision severity increases dramatically with speed.
A 1000 kg car at 60 km/h (16.7 m/s) has about 139 000 J (139 kJ) of kinetic energy — equivalent to lifting the same car 14 metres off the ground. At 120 km/h the energy quadruples to 556 kJ.
In thermodynamics, the kinetic energy of gas molecules is directly proportional to absolute temperature (kT = ½mv²). In projectile physics, muzzle energy is often quoted in joules.
Frequently asked questions
The calculator shows the height from which the object would need to be dropped to acquire the same kinetic energy. It comes from equating KE to gravitational potential energy: h = KE ÷ (mg). This puts the energy in intuitive context.
No. Kinetic energy is a scalar quantity — it depends on speed (magnitude of velocity), not direction. Two objects of the same mass moving at the same speed in opposite directions have the same kinetic energy.
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