The essentials
The kinetic energy of an object is KE = ½mv². Mass is measured in kilograms and speed in metres per second to obtain energy in joules.
Because speed is squared, doubling speed multiplies kinetic energy by four when mass is unchanged.
Worked example
For a 2 kg object moving at 3 m/s:
KE = ½ × 2 × 3² = 9 J.