½mv²Kinetic Energy Calculator
Kinetic energy is the energy possessed by an object due to its motion. It depends on both mass and the square of velocity — doubling speed quadruples kinetic energy, while doubling mass only doubles it. KE is the work-energy theorem in action: the net work done on an object equals the change in its kinetic energy.
- 1KE = ½mv² (joules, J)
- 2m = mass in kg, v = velocity in m/s
- 3Momentum p = mv (kg⋅m/s) — conserved in collisions
- 4Work done to bring to rest = KE (e.g. braking distance calculation)
- 5KE is scalar (no direction); momentum is a vector
70 kg person running at 10 m/s (36 km/h)=KE = ½ × 70 × 100 = 3,500 JEquivalent to lifting ~350 kg by 1 metre
1,500 kg car at 30 m/s (108 km/h)=KE = 675,000 J = 675 kJExplains why speeding is so dangerous
0.006 kg bullet at 900 m/s=KE = 2,430 J — more than a running person
| Object | Mass | Speed | KE |
|---|---|---|---|
| Bullet (.308) | 10 g | 900 m/s | 4,050 J |
| Cricket ball (fast bowl) | 0.16 kg | 44 m/s | 155 J |
| Person walking | 70 kg | 1.5 m/s | 79 J |
| Car at 60 mph | 1,500 kg | 26.8 m/s | 538 kJ |
| Loaded lorry at 60 mph | 44,000 kg | 26.8 m/s | 15.8 MJ |
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