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How It Works
Kinetic energy is the energy an object has because of its motion: K = ½mv². Doubling the speed quadruples the energy, which is why high-speed collisions are so much more destructive. You can rearrange the equation to solve for mass or velocity when the other values are known.
Example Problem
A 1,500 kg car travels at 25 m/s. What is its kinetic energy?
- K = ½ × 1,500 × 25² = 0.5 × 1,500 × 625
- K = 468,750 J (about 469 kJ)
Frequently Asked Questions
Why does kinetic energy depend on velocity squared?
The work needed to accelerate an object grows with velocity. Each additional m/s of speed requires more work than the last because the object covers more distance per second while the force is applied.
What is the difference between kinetic and potential energy?
Kinetic energy is energy of motion (½mv²). Potential energy is stored energy due to position or configuration (e.g., mgh for gravity). They can convert back and forth, as in a pendulum swing.
Can kinetic energy be negative?
No. Both mass and the square of velocity are always non-negative, so kinetic energy is always zero or positive.
Related Calculators
- Potential Energy Calculator — find gravitational potential energy (mgh).
- Work Calculator — calculate work done by a force.
- Impulse & Momentum Calculator — relate force, time, and momentum change.
- Force Equation Calculator — the net force that accelerates objects to kinetic energy.
- Power Calculator — rate of energy transfer related to kinetic energy change.
- Energy Unit Converter — convert between joules, calories, BTU, and more.
Reference: Lindeburg, Michael R. 1992. Engineer In Training Reference Manual. Professional Publication, Inc. 8th Edition.