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Homework Help: Ultimate strength

  1. Oct 3, 2006 #1
    A solid steel ball is hung at the bottom of a steel wire length 2 meters and radius of 1mm. The ultimate strength of steel is 1.1 X 10^9 N/m^2. What is the mass of the biggest ball the wire can bare.

    This seems like a pretty straight forward question. I am guessing the 2 meter radius doesn't matter. I am thinking that you need to find the area of a cross section of the 1mm wire. I am not sure what to do next.

    2nd part ... what is the period of torsional oscillation of the system?
    The shear modulus of steel = 8x10^10 N/m^2 and the interia is (2MR^2)/5.

    Here I think you need to use the equation... T = 2pi * (I/c)^.5 where C is the shear modulus. I can't figure this part out. Do i need to worry about the cross sectional area here also?

    Thank you very much everyone!
  2. jcsd
  3. Oct 3, 2006 #2
    Let's say you found the area of the cross-section to be A. Well, if it is [tex] \frac{1.1 \times 10^9}{1m^2}[/tex], how much is it for [tex]\frac{x}{A}[/tex]. And notice that this is not the final answer. It will give you the maximum force that that specific thickness of steel wire can resist.
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