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Homework Help: What is your friends speed relative to you?

  1. Dec 17, 2007 #1
    1. The problem statement, all variables and given/known data

    There's a 100m wide river, with a current of 8.5 m/s going 45 degrees SE. You and a friend are standing directly opposite each other across the river, the friend on the north side, you on the south side. You each get in boats that travel 7 m/s relative to the water and head out directly north/south.

    a. What is your friends speed relative to you?

    d. How long does it take to cross the river?

    2. Relevant equations

    3. The attempt at a solution

    Just looked over briefly at some of them, can someone verify if these look correct?

    A is 14 m/s

    D Since you will be traveling 1 m/s north (the current vector will push 6 m/s down on you), it will take 100 s to cross it.
  2. jcsd
  3. Dec 17, 2007 #2


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    Homework Helper

    looks fine to me
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