Physics
Kinetic energy from mass and speed
The standard form. Square the speed first, then multiply by mass and halve. The speed must be in metres per second.
The Formula
KE = 1/2 m v^2
The standard form. Square the speed first, then multiply by mass and halve. The speed must be in metres per second.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| m | Mass of the moving object | kilograms | In kilograms. Using grams by mistake inflates the answer a thousandfold. |
| v | Speed of the object | metres per second | In metres per second; divide a km/h figure by 3.6 before substituting. |
| KE | Kinetic energy | joules | A scalar measured in joules, with no direction attached. |
What Each Symbol Means
mkilograms
Mass of the moving object
In kilograms. Using grams by mistake inflates the answer a thousandfold.
vmetres per second
Speed of the object
In metres per second; divide a km/h figure by 3.6 before substituting.
KEjoules
Kinetic energy
A scalar measured in joules, with no direction attached.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate kinetic energy page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Kinetic Energy, filed under Science. Every number the guide produces comes from substituting into this one line.