Speed
The distance that an object travels per unit of time is called speed. To determine speed, use the formula below:
\[
\text{speed} = \frac{\text{distance}}{\text{time}}
\]
or in symbols,
\[
v = \frac{d}{t}
\]
The rate of motion or the speed of an object is commonly expressed in meters per second (m/s), centimeters per second (cm/s), or kilometers per hour (km/h).
For example, if a car travels 100 km in 2 h, its speed is
\[
\begin{align*}
v &= \frac{d}{t} \\
&= \frac{100\, \text{km}}{2\, \text{h}} \\
&= 50\, \text{km/h}
\end{align*}
\]
50 km/h represents the car’s average speed, or the total distance traveled divided by the total time to cover such distance. Average speed may be faster at the start or at the end of the travel than during the middle part of the travel.
