Kinetic Energy Calculator

Velocity is Squared - Small Speed Changes Matter

Going from 100 to 110 km/h doesn't add 10% more kinetic energy - it adds 21% more. The v² means energy grows way faster than speed. This is why speed limits exist and why engineers design crumple zones. More speed = exponentially more energy to manage in a crash.

Units Matter (m/s, Not km/h)

Mass must be in kilograms, velocity in meters per second. You can't use km/h without converting first (divide by 3.6 to get m/s). Common physics homework mistake: plugging in 100 km/h instead of 27.8 m/s and getting a wildly wrong answer.

Kinetic Energy is Always Positive

Direction doesn't matter for kinetic energy. Moving left at 10 m/s has the same kinetic energy as moving right at 10 m/s. The v² makes negative velocities positive. Zero motion = zero KE. Any motion = positive KE.

Forgetting to Square the Velocity

"KE = ½mv, right?" - No! It's ½mv². Forgetting to square velocity is the #1 physics homework mistake. A car at 20 m/s doesn't have twice the energy of one at 10 m/s - it has 4× the energy (20² vs 10²).

Why it happens: People remember "half mass velocity" and forget the squared part.
Fix: Always write v² in your formula. Check your work - does doubling speed quadruple your answer?

Using km/h Instead of m/s

Velocity needs to be in m/s, but your car speedometer shows km/h. Using 100 km/h directly instead of converting to 27.8 m/s gives you an answer that's off by a factor of 13. Always convert first.

Real consequence: Your physics homework gets marked wrong.
Fix: km/h ÷ 3.6 = m/s. 100 km/h = 27.8 m/s.

Confusing Kinetic and Potential Energy

A ball sitting on top of a hill has potential energy (could fall), not kinetic energy (not moving). Once it rolls down, that potential converts to kinetic. At rest at the top = potential. Moving at the bottom = kinetic.

How to remember: Kinetic = moving. Potential = could move (but isn't yet).

What is kinetic energy?

Kinetic energy is the energy of motion. Anything moving has it. A rolling ball, a flying bird, a driving car - they all have kinetic energy. The faster it moves or the heavier it is, the more kinetic energy it has. Formula: KE = ½mv² (half the mass times velocity squared).

Why is velocity squared in the formula?

Because energy increases exponentially with speed. Drive twice as fast (2x velocity) and your car has 4x the kinetic energy (2² = 4). That's why high-speed crashes are so much more destructive - doubling your speed quadruples the energy you need to dissipate when you stop.

What's the difference between kinetic and potential energy?

Kinetic energy is energy of motion (moving). Potential energy is stored energy (position). A ball at the top of a hill has potential energy. Roll it down and that converts to kinetic energy. At the bottom it's all kinetic. They transform back and forth.

How much kinetic energy does a car have?

Example: A 1500 kg car at 100 km/h (27.8 m/s). KE = ½ × 1500 × 27.8² = 579,000 Joules (579 kJ). That's the energy it takes to accelerate the car to that speed, and the energy the brakes have to dissipate to stop it.

Can kinetic energy be negative?

No. Kinetic energy is always positive or zero. Even if velocity is negative (moving backwards), you square it in the formula, which makes it positive. Zero velocity = zero kinetic energy. Any motion = positive kinetic energy.