Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
The same cyclist rides from town A to town B and back to town A. What is her average velocity for the whole round trip?
Speed distance time; velocity displacement time. Average speed total distance total time. .
Distance is the length of the whole path; it has no direction and never decreases. Displacement is the straight line from start to end, with a direction. On a straight road use signs; for a right-angle turn, displacement .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Displacement. She ends where she started, so her displacement is zero.
Step 2. Average velocity. .
Answer: .
Check. Her average speed was ; her average velocity is zero. They differ because she turned back.
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