Kinetic Energy
The energy an object has because of its motion.
KE = \dfrac{1}{2}mv^2
1What it means
Kinetic energy depends on the square of speed, so doubling the speed gives four times the energy. It is measured in joules (J).
2Variables
| Symbol | Meaning |
|---|---|
| KE | Kinetic energy (joules, J) |
| m | Mass (kg) |
| v | Speed (m/s) |
3Worked examples
Example 1 Worked solution
Q. Find the kinetic energy of a 2 kg ball moving at 10 m/s.
- KE = ½ m v² = ½ × 2 × 10².
- = 1 × 100.
✓ KE = 100 J
4Where it's used
- ✦Vehicle safety and stopping-distance analysis.
- ✦Energy in moving machinery and projectiles.
5Tips & common mistakes
- !Square the speed before multiplying.
- !Because of the square, speed matters far more than mass for energy.