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Boat hauling skier

  1. Jul 30, 2008 #1
    1. The problem statement, all variables and given/known data

    A boat is hauling a 250kg skier at an angle of 30 degrees below the horizontal with a force of 200 N. How much is the boat accelerating?

    2. Relevant equations

    3. The attempt at a solution

    I am using the F=ma equation. My only question is how does the 30 degrees play into it? Would it be :

    200N= 250kg(cos30) * a? with this I get .03m/s. Which seems somewhat accurate since 200N isnt much force at all. Any ideas?
  2. jcsd
  3. Jul 30, 2008 #2


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    Assuming the 200N force means in the direction of the cable (ie 200N of tension) then then horizontal force on the skier (and so on the boat) is
    200N cos(30) = 173N

    Then F = ma ,
    173 = 250 a
    a= 0.69m/s^2

    edit - google calculator uses rad for trig functions !!!!!
  4. Jul 30, 2008 #3
    Ok. Thanks. That makes sense. At least I had the right equation. Thanks for your help. The 30 degrees threw me off.
  5. Jul 30, 2008 #4


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    Instead of remembering cos / sin etc it's better to picture what's happening

    If the rope is horizontal (angle=0) then all the force is being used to slow the boat, as the rope drops less force is being applied horizontally, so you need a trig function that starts at 1 for 0 degrees and slowly gets less = cos()
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