Utilnaro

Work, energy and power

Kinetic energy

Calculate translational kinetic energy, mass, or speed using the classical relationship between mass and motion.

Formula

Ek=12mv2 Ek = 1/2 × m × v²

Translational kinetic energy equals one half of the mass multiplied by the square of speed.

Kinetic energy calculator

What do you want to calculate?

Known values

The result updates when a value changes.

Result

50 kJ

Substitution and calculation

Eₖ = m × v² / 2 = 1,000 kg × (10 m/s)² / 2 = 50,000 J

Unit conversion: 50,000 J = 50 kJ

Symbols and units

SymbolQuantitySISupported units
Ekkinetic energyEnergy associated with the translational motion of the object.JJ, kJ
mmassMass of the moving object.kgkg, g
vspeedSpeed of the object relative to the selected frame of reference.m/sm/s, km/h

Formula rearrangements

Calculate kinetic energy

Ek = 1/2 × m × v²

Calculate mass

m = 2 × Ek / v²

Calculate speed

v = √(2 × Ek / m)

Worked examples

Kinetic energy of a car

A car with a mass of 1500 kg travels at 20 m/s. Calculate its kinetic energy.

  1. 1Step 1: Square the speed: 20² = 400.
  2. 2Step 2: Multiply 1/2 by 1500 kg and 400 m²/s².
  3. 3Step 3: The result is 300000 J, or 300 kJ.

Result: 300,000 J (300 kJ)

Kinetic energy of a baseball

A 145 g ball moves at 40 m/s. Calculate its kinetic energy.

  1. 1Step 1: Convert 145 g to 0.145 kg.
  2. 2Step 2: Square the speed: 40² = 1600.
  3. 3Step 3: Multiply 1/2 by 0.145 kg and 1600 m²/s² to obtain 116 J.

Result: 116 J

Sources and review