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Kinetic Energy Calculator

Find the kinetic energy of a moving object.

Result

375,000.00

How it is calculated

Kinetic energy is the energy an object has because it moves: E = ½ × m × v². m is mass in kilograms, v is speed in metres per second and the result is in joules (J). Because speed is squared, doubling the speed quadruples the energy, while doubling the mass only doubles it. A negative velocity gives the same result as a positive one (only the speed matters, not the direction), but a negative mass is rejected. The result is rounded to two decimals. Relativistic speeds close to that of light are outside the scope of this classical formula.

Worked example

A car of 1,200 kg moving at 25 m/s (90 km/h). Square the speed: 25² = 625. Multiply by mass: 1,200 × 625 = 750,000. Take half: 375,000.00 J, or 375 kJ. If the speed rose to 50 m/s (180 km/h), the energy would be four times bigger, 1,500,000 J, which is why braking distance grows so quickly with speed.

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Common mistakes

  • Entering speed in km/h. The formula needs m/s, so 90 km/h must be converted to 25 m/s first; otherwise the answer is about 13 times too large.
  • Forgetting that velocity is squared and expecting energy to double when speed doubles.
  • Entering mass in grams or tonnes instead of kilograms.
  • Forgetting the factor ½ and getting twice the correct energy.

About this calculator

This calculator applies the classical mechanics formula KE = ½mv², where energy grows with the square of velocity — doubling speed quadruples the kinetic energy, not just doubles it. It's the same relationship that makes high-speed collisions so much more destructive than low-speed ones.

It's used by physics students solving textbook problems, automotive engineers estimating crash-impact energy for safety testing, ballistics enthusiasts calculating projectile energy, and roller-coaster designers checking that cars carry enough energy through a loop.

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Comments (1)

  • Editorial team

    Kinetic energy is what a braking system has to remove, so it helps explain stopping distances. With the same braking force, stopping distance grows in proportion to the energy, which means about four times the distance when speed doubles. Convert km/h to m/s before entering, dividing by 3.6. The tool gives joules only and ignores friction, air drag and slopes. Tell us which everyday situation you are checking, such as a cyclist, a car or a thrown ball.

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