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Homework Help: Elastic properties of solids problem

  1. Dec 14, 2014 #1
    1. The problem statement, all variables and given/known data
    If the shear stress in steel exceeds about 4.0 x 10^8 N/m^2, the steel ruptures. Determine the shear force necessary to punch a 1-cm diameter hole in a steel plate that is 0.5 cm thick.

    2. Relevant equations

    3. The attempt at a solution

    The way I tried to solve this problem was by doing

    4.0 x 10^8 N/m^2 = x/((.005^2)*3.14*.005)

    and solving for x, where x is the amount of newtons necessary to punch the hole in the steel plate. I did this because the ratio of Newtons to m^2 must be 4.0 x 10^8 N/m^2. So I found the area of the plate punched out and solved for x. The solution to this problem is 6.28 x 10^4 N and I got 157 N.

     
  2. jcsd
  3. Dec 14, 2014 #2
    What is the surface area of the hole?
     
  4. Dec 15, 2014 #3
    The surface area of the hole should be 7.85 x 10^-5 m^2.
     
  5. Dec 15, 2014 #4

    haruspex

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    That's not what I get. How are you calculating it?
    You are told the diameter and the depth, and you want the surface area inside the hole.
     
  6. Dec 24, 2014 #5
    Ok I realized my mistake. Thanks!
     
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