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I don't know how to do this. It looks simple but

  1. Jan 13, 2008 #1
    1. The problem statement, all variables and given/known data
    A rope is tied to a tree 10 feet up, and held out horizontally.
    A diagonal post rests at the bottom of the tree and goes up at a 60 degree angle. At a height of 10 feet the rope intersects the diagonal post and they are tied together. This creates a 30/60/90 triangle of tree, rope, and diagonal post. The force on the rope is away from the tree, The force on the diagonal post is down towards the base of the tree.

    If a weight of 200 lbs is hung from the intersection of the rope and the post, what is the tension on the rope and what is the pressure on the bottom of the tree?


    2. Relevant equations



    3. The attempt at a solution
    I am missing a couple of issues here. I tried using trig on the vectors but I seem to be missing a value. Help.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 13, 2008 #2

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    Suppose T is the tension in the rope, W the weight hanging, and P is the force on the post. At the pt where the weight is hanging, these three concurrent forces are in equilibrium. That's the starting point.
     
  4. Jan 13, 2008 #3
    Sorry, my knowledge of vectors is all self taught and rudimentary, I don't know what equilibrium is.
     
  5. Jan 13, 2008 #4

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    Equilibrium is when the net force on an object is zero, and the net moment of all the forces about any point is zero. In other words, the object does not move or rotate (for simplicity, wrt the earth.)

    What do know then? Can you resolve forces into horizontal and vertical directions?
     
  6. Jan 13, 2008 #5
    I'm sorry, but I seem to be ignorant of basic terminology.

    I THINK I can resolve forces in horizontal and vertical directions. I understand adding a negative force to a positive in a straight line results in a reduced force. Where I seem to break down, is when a force divides and when it goes off at a different angle. Another one that I can't do is if you have two unequal vectors away from the same point. I can figure the direction of the resultant vector but not the magnitude. I appreciate the help and if the appropriate thing to do is send me to a tutorial, let me know.
     
  7. Jan 14, 2008 #6

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    I think you must go to a tutorial. Best wishes.
     
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