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Math Help - Physics question

  1. #1
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    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...
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  2. #2
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    Quote Originally Posted by Phoebe83 View Post
    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...
    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
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