Velocity

Velocity is the measurement of speed included with a direction. Both speed and direction are measured relative to some fixed object (in most cases, our planet earth). The numerical value of speed can be represented as a negative, which would indicate the opposite direction as indicated.

Equation

Velocity can be calculated from by the following expression:

$\overrightarrow{v}=\frac{\mathrm{\Delta }\overrightarrow{x}}{\mathrm{\Delta }t}$

The arrow above the velocity variable v indicates that it is a vector variable, and has some direction.

Velocity unit converter

Please see below to convert among various units for velocity:

Examples

The train was moving at 50 km/h west.

• 50 km/h represents the speed
• West indicates the direction.

The Frisbee was thrown with a horizontal velocity of 10 m/s

• 10 m/s represents the speed
• the direction is horizontal, meaning the speed measurement is not accounting for the speed the Frisbee is falling

After the accident, the car was traveling at a velocity of -2 km/h

• The speed of the vehicle is 2km/h
• The direction would be the opposite direction which the vehicle is facing (intuitive deduction)

Hyperphysics has a more detailed discussion of velocity.

For Further Reading

• Energy
• End use energy
• Primary energy
• Energy conversion technology
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