### Introducing Calculus

Building blocks

In Discussing distance we mentioned speed and velocity. Average speed is the rate your distance changes in a set period of time, for example $\quantity{50}{km}$ in $1$ hour. If you walk to school you will speed up, slow down, perhaps even stop. Your speed will not stay the same, but we can talk about your average speed for the trip.
Velocity is similar but, like displacement, also depends on direction. If you average $\quantity{3}{km/h}$ on your walk to school, and walk home in the same amount of time, your velocity for the return part of your journey would be $\quantity{-3}{km/h}$.