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Finding minimum values for problems

  1. Aug 2, 2013 #1
    1. The problem statement, all variables and given/known data
    Hi guys, really stuck on this one.

    A 1000N black is to be lifted using a chain sling (as shown). If the tension in the chain sling is not to exceed 1300N, find the shortest sling ABC that can be used.
    A is the most left point, B is the most right point and C is the top point.




    2. Relevant equations



    3. The attempt at a solution

    I think i have to take the derivative of something to find the minimum but have no idea how to go about that.

    Picture_2.jpg
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Aug 2, 2013 #2

    gneill

    User Avatar

    Staff: Mentor

    You shouldn't need to use calculus on this one. Since you've been given the maximal value of the tension, start by writing an expression that gives the tension in the sling as a function of the angle where the sling meets the block. What is the value of the angle that corresponds to the given maximal tension?
     
  4. Aug 3, 2013 #3
    I think i've got it.

    With this formula
    T sin(theta) = W/2
    i can get the angle cause i know the max tension, but then how do i get the length of the chain from that?
     
  5. Aug 3, 2013 #4

    gneill

    User Avatar

    Staff: Mentor

    If you know the angle and at least one triangle side length...
     
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