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Simple work problem

  1. Apr 8, 2015 #1
    1. The problem statement, all variables and given/known data
    A 70.0 kg sailor climbs an 11.5 m long rope ladder to a mast above at constant velocity. The rope ladder is at an angle of 30.0° with the mast. Assume that the ladder is frictionless. How much work does the sailor do?

    2. Relevant equations
    ##W = Fd##


    3. The attempt at a solution

    ##F_{net||} = F_{a} + F_{g||}##
    ##F_{a} = -F_{g} = -mg\sin \theta##
    ##W = F_{a}d##
    ##W = -mgd\sin \theta##
    ##W = -(70kg)(-9.8m/s^{2})(11.5m)0.5##
    ##W = 515 J##

    However, in the solution manual, this is not the correct answer. What am I doing wrong?
     
  2. jcsd
  3. Apr 8, 2015 #2

    SammyS

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    The angle, θ, that you used is with respect to the deck, so it's not 30° .

    That is to say, if you use sin(θ) that is with respect to the deck.
     
    Last edited: Apr 8, 2015
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