Impact Energy Calculator

Calculate the force and energy involved with impact loads using our impact energy calculator.

Kinetic energy1 kJ½ × 5 kg × (20 m/s)²

Potential energy980.665 J5 × 9.8067 × 20

Total mechanical energy1.9807 kJ

Work done by the force3 kJforce and motion are aligned, so all of it counts

Power375 W0.5029 horsepower

Power to reach this kinetic energy125 W

Speed this potential energy would give19.8057 m/sif it all became kinetic — the free-fall result

Height this kinetic energy would reach20.3943 mif it all became potential

Kinetic energy at twice the speed4 kJfour times as much — energy goes as the square of speed, which is why stopping distances grow so fast

In kilowatt-hours0.00055018 kWh

In food calories0.47339 kcal

The formula

KE = ½mv², PE = mgh, W = Fd cos θ, P = W ÷ t

Work needs motion along the force

Work is force times distance, but only the component of force pointing along the motion counts — hence the cosine. Carry a heavy box across a level floor and you do no work on it in the physics sense: the force you apply is upward, the motion is horizontal, and the angle between them is 90°, whose cosine is zero. Your muscles tire because they are doing internal work, not because the box is gaining energy.

Kinetic energy grows with the square of speed while momentum grows linearly. Doubling speed doubles momentum but quadruples energy, and since braking dissipates energy over distance, it quadruples the stopping distance too. This is the single most important quantitative fact in road safety.

Potential and kinetic energy are interconvertible, which is why √(2gh) appears both as the speed gained in a fall and as the speed needed to rise to a height. The two expressions are the same statement of conservation read in opposite directions.