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Homework Help: Position equation with vectors

  1. Jul 17, 2008 #1
    1. The problem statement, all variables and given/known data
    Mary needs to row her boat across a 100 m wide river that is flowing to the east at a speed of 1.0 m/s. Mary can row the boat with a speed of 2.0 m/s relative to the water.

    2. Relevant equations
    pythagorean theorem: a^2+b^2=c^2

    3. The attempt at a solution

    Ok so I know this is pretty straight forward problem. But the 100 m is throwing me off here. I draw a vector diagram and add the two component vectors:


    Now i used pythagorean theorem to find the resultant 1^2 + 2^2 = R^2, in which R=5^1/2=2.2. So she's moving accross the river at a rate of 2.2 m/s. Now I'm not sure how 2.2 m/s and 100 m finds her displacement. Any tips?
  2. jcsd
  3. Jul 17, 2008 #2
    never mind got it figured out.
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