# How do I find average velocity?

Jun 10, 2015

You divide total distance by total time.

#### Explanation:

Sometimes you first have to work out separate distances or times and then add them before you can work out the average.

Example:
I travel to Amsterdam (which is not my favourite city) to deliver a parcel and I do the 60 km distance at an average speed of 60 km/h (last part of rush hour). After that I speed back to my favourite town at an average of 120 km/h.

My average speed on the whole trip is NOT :

$\overline{v} \ne \left(60 + 120\right) / 2$ which would be 90 km/h

The correct calculation is as follows:
The trip to A took me 1 hour, the trip back only 1/2 hour.

$\to \overline{v} = \frac{2 \cdot 60 k m}{1.5 h} = 80 k m / h$

This may go against your intuition, but remember, I spent much more time driving slow, than I did driving fast.