### Sample question

On your way to class, you leave home and walk at 3 m/s east towards
campus.

After one minute, and after covering 180 m, you realize that you left your
physics assignment at home, so you turn around and run, at 6 m/s, back to get
it. You're running twice as fast as you walked, so it takes 30 seconds to get
home again.

For the 90 second out-and-back trip, what is your average speed?

- 4 m/s
- 4.5 m/s
- 5 m/s

The average speed is the total distance covered divided by the total time.

That works out to 360 m / 90 s = 4 m/s

What is your average velocity?

- zero
- 1.5 m/s West
- 3 m/s West
- 4 m/s West
- none of the above

Average velocity is the net displacement divided by the total time.

Since the net displacement is zero, **v**_{avg} = 0.