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Homework Help: Work done and angle

  1. Jul 13, 2012 #1
    1. The problem statement, all variables and given/known data
    1. A small plane tows a glider at constant speed and altitude. If the plane does 2.00 x 105 J of work to tow the glider 145 m and the tension in the tow rope is 2560 N, what is the angle between the tow rope and the horizontal?

    2. Water skiers often ride to one side of the center line of a boat as shown below. In this case, the ski boat is travelling at 15 m/s and the tension in the rope is 75 N. If the boat does 3500 J of work on the skier in 50.0 m, what is the angle θ between the tow rope and the center line of the boat?

    2. Relevant equations
    W = F d cos θ
    W = Δ KE

    3. The attempt at a solution
    W = F d cos θ
    2 x 105 = 2560 x 145 cos θ
    θ = 57.4o
    I'm not sure because I don't know the picture of plane tows a glider. I am only using the formula

    W = F d cos θ
    3500 = 75 x 50 cos θ
    θ = 21.04o
    Is the speed given in the question not important?

  2. jcsd
  3. Jul 13, 2012 #2


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    All looks good to me. The speed is irrelevant in part b.
  4. Jul 14, 2012 #3


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    and me. Speed irrelevant in both parts as the problem is the same.

    Speed information would have be needed had the question given you "power" rather than "work".
  5. Jul 14, 2012 #4
    Thanks :smile:
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