First off I would like to say hi to everyone!

I am taking Engineering Physics and right now I down right suck at it and simple things seem to confuse me. Its been 13 years since any math class which the last one was Calculus I. So as you can see I am pretty rusty and trying to teach myself math again (and believe me I forget some really simple rules at times) as I move through physics. I have bought some videos from Math Tutor, on Physics and Math to try and help but its tough fight at this early stage.

just for the record we are graded on homework for doing it not on its content. Meaning the professor has the solution guide which is free for us to use in the library (soon as it gets in they changes books this semester).

So when I ask for help on book questions this is not breaking the rules as we are not graded on this portion at least in that manner they are just considered practice problems not if they are right or wrong.

My first question seems so simple but I cannot figure out how the book has the the answer it is as follows:

A person walks first at a constant speed of 5.00m/s along a staright line from a point A to B and then back along the line from B to A at a constant speed of 3.00m/s.

(a) What is her average speed over the entire trip?

(b) what is her Average velocity over the entire trip?

(a) = 3.75m/s (I dont know how they got this answer its killing me!

(b) = 0 this I knew the answer to before looking for the following reason in the book they give the following example:

A runner who runs a distance d of more than 40km and yet ends up at her starting point. her total displacement is zero, so her average velocity is zero!

I guess in my thinking (b) means (xf - xi)/(tf - ti) since its displacement they started out at zero then ended back up at zero and zero decided by anything is zero. Thus velocity is zero.

Where as if it was average speed has no direction and is always expressed as a positive number xf = some amount and xi = 0 So it would be the total amount traveled decided by time. So I think I have question (b) down.. I hope...

However on (a) I am stumped! its irritating becaues it seems like it has to be so simple but I am missing it

Thanks,

Brian