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Homework Help: Car Physics Problem

  1. Oct 24, 2007 #1
    Car Vector Displacement Problem

    1. The problem statement, all variables and given/known data
    A car moves 65km due east, then 45km due west. What is the total displacement?

    2. Relevant equations
    Don't understand what you mean. =/

    3. The attempt at a solution
    What I did was... 45km/65km to find the degree, and I got 34.7
    So I used cosine, Cos(34.7)x65km which equal the total displacement, I got 53.44km
    Last edited: Oct 24, 2007
  2. jcsd
  3. Oct 24, 2007 #2


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    Homework Helper
    Gold Member

    I am not sure what you are trying to do there. 45/65 is not 34.7 and that will not give you an angle. When asked for net displacement, you are being asked, "How far from the starting point does the guy end up?"

    Think about this. The guy moves 65km east, then turns around and moves 45 km in the opposite direction. Draw this situation and you should be able to visualize the situation a little more clearly.
    Last edited: Oct 24, 2007
  4. Oct 24, 2007 #3
    if you take two steps forward and one step back you have gone one step forward.

    This guy has gone 65km east then back 45km, so he has gone 65km-45km
  5. Oct 24, 2007 #4
    So is that how you find the total displacement? I'm looking at my textbook, but it doesn't really explain total displacement.

    The textbook I have is: Glencoe Science: Physics Principles and Problems
  6. Oct 24, 2007 #5
    Displacement is the length of the the line segment connecting the starting point to the ending point.
  7. Oct 28, 2007 #6
    More accurately and importantly, it is a vector quantity. If the point of origin is the starting point, and east is taken as the positive direction, its displacement is 20m at 0 degrees from the horizontal, or any other way you want to express a vector.
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