Average speed

1. May 14, 2013

xzibition8612

1. The problem statement, all variables and given/known data

A person walks first at a constant speed 5m/s along a straight line from point A to point B, and then back along the line from B to A at a constant speed 3m/s. (a) What is her average speed over the entire trip? (b) Her average velocity over the entire trip?

2. Relevant equations

Average speed = total distance traveled / total time

3. The attempt at a solution

(b) is obviously 0 since start and end positions are the same. For (a), the book gives the answer 3.75m/s. No idea how this came about. Since no time was given, how do you get this answer???

2. May 14, 2013

Staff: Mentor

The average speed is (total distance)/(total time).

If you let d = the distance from A to B, what expression represents the time for her to go from A to B?
What expression represents the time for her to make the return trip?

3. May 14, 2013

xzibition8612

d/5 = time from A to B
d/3 = time from B to A

k i figured it out thx for ur help