Physics question

Hi everyone!

I just started to study physics and there is something I don't understand.

average velocity is the displacement (Delta X) divided by time(Delta t), right ?

so, if a car drives from A to B (say in 2 minutes) and back from B to A (in 5 minutes) it's displacement (Delta X) for the entire trip is 0 because it return the same place...
(if we draw a graph of X(t) and we draw a line between the start point and the end point - the slope of that line represents the average velocity, am I right?)

so the average velocity is 0 ??
please enlighten me...

Quote:

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Originally Posted by Phoebe83

Hi everyone!

I just started to study physics and there is something I don't understand.

average velocity is the displacement (Delta X) divided by time(Delta t), right ?

so, if a car drives from A to B (say in 2 minutes) and back from B to A (in 5 minutes) it's displacement (Delta X) for the entire trip is 0 because it return the same place...
(if we draw a graph of X(t) and we draw a line between the start point and the end point - the slope of that line represents the average velocity, am I right?)

so the average velocity is 0 ??
please enlighten me...

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That is exactly correct. Don't confuse the average velocity with the average speed:
average velocity = displacement/time
average speed = distance/time

The average speed is NOT simply the magnitude of the average velocity vector as many students assume. Furthermore, many texts and professors use the terms incorrectly so there is much room for confusion.

-Dan