Kinetic Energy & Momentum Calculator
Kinetic energy represents the energy possessed by an object due to its motion. Calculate vehicle impact energies, ballistics energy, sports dynamics, and physics problems.
How it works
Because velocity is squared ($v^2$), doubling an object's speed quadruples its kinetic energy and braking distance requirement.
Formula
KE = (1 / 2) m v^2, p = m × v, 1 kJ = 1000 J
Calculates the mechanical work needed to accelerate a body from rest to its stated velocity, scaling with mass and the square of velocity.
| Symbol | Variable | Unit | Description |
|---|---|---|---|
| m | Mass of the moving object | kg | |
| v | Magnitude of instantaneous velocity | m/s | |
| KE | Translational kinetic energy | J | |
| p | Linear momentum vector magnitude | kg·m/s |
Worked example
1,200 kg car traveling at 20 m/s (72 km/h)
- Mass:
- 1,200 kg
- Velocity:
- 20 m/s (72 km/h)
KE = 0.5 × 1,200 × (20)² = 0.5 × 1,200 × 400 = 240,000 Joules (240.00 kJ). Momentum p = 1,200 × 20 = 24,000 kg·m/s.
Limitations
Does not include rotational kinetic energy (KE_rot = 0.5 × I × ω²) of spinning wheels or flywheels.
Frequently asked questions
Why does speeding drastically increase collision severity?
Kinetic energy scales with velocity squared. Increasing driving speed from 60 km/h to 120 km/h (2× speed) increases kinetic impact energy and crash destruction by 4× (400%).
What is the difference between Kinetic Energy and Momentum?
Momentum (p = m × v) is a vector quantity that is conserved in all collisions. Kinetic energy (KE = 0.5 × m × v²) is a scalar measure of work and is only conserved in perfectly elastic collisions.
How do I convert Joules to Foot-Pounds or Calories?
1 Joule ≈ 0.73756 ft-lb ≈ 0.2390 calories (0.000239 kcal).
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Last reviewed: 2026-08-22.