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Homework Help: Help needed on another force problem!

  1. Dec 7, 2005 #1
    An object of mass 20.0 kg hangs suspended from a hook that is attached to two wires. The wires are attached to a horizontal cross bar and make angles with it that open up to 25 degrees and 50 degrees. What is the tension on each wire?
  2. jcsd
  3. Dec 8, 2005 #2
    Start with a Free-Body-Diagram.
  4. Dec 8, 2005 #3
    force body diagram.GIF

    Here is the force body diagram as complete as I could make it. I do not know how to figure out what any of the other forces are.
  5. Dec 8, 2005 #4
    I cant see it until its approved, Just describe what you drew.
  6. Dec 8, 2005 #5


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    start with components. The box is at equilibrium, so the sum of all the forces = 0 in each direction.

    y comp = sin(theta)
    x comp = cos(theta)
  7. Dec 8, 2005 #6
    Well, its a little odd to put that normal force there in your problem. What you really have is just two tensile forces acting up along the axis of the two cables. So, 2 tensile forces, and erase that normal force.
  8. Dec 8, 2005 #7
    There will be no normal force.
    Now balance the forces in horizontal and vertical direction.
    Suppose Tension is T1 in first wire and T2 in second wire
    T1 cos(50) = T2 cos(25)
    T1 sin(50) + T2 sin(25) = Mg

    Now try to solve.

  9. Dec 8, 2005 #8
    Please dont give him completed solutions anymore....

    can you delete that post.
  10. Dec 8, 2005 #9
    I haven't given complete solution...and I am sure he would have done the same
  11. Dec 8, 2005 #10
    At least let im learn how to set up the equations so that he has some understanding of why hes using them. Certainly you can see my point. He is still trying to develop an understanding of forces. Thats why I told him to start off with a FBD and work one step at a time to build some knowledge.
  12. Dec 8, 2005 #11
    okay ....I think he will not copy the equation...but will try to understand how to write equations.....
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