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Homework Help: What maximal load can be lifted from a depth of 1000 m ?

  1. Aug 16, 2006 #1
    A steel rope consists of 100 rods. The diameter of each rod is 2 mm. The allowable rope stress is 130 N/mm^2.

    what maximal load can be lifted from a depth of 1000 m ?

    i use 100*130 N/mm^2 = 4*F(max) / pi * (4)

    in order to find F(max).Am i correct??how can i use the length given??

  2. jcsd
  3. Aug 16, 2006 #2


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    One cannot multiply the stress by the number of rod. The stress in each rod is a maximum of 130 N/mm2.

    Each rod can carry a load, so F = Stress * area, then F(rope) = 100 * F(rod). However, the steel rope must lift its weight (mass), so one has to subtract the weight of 1000 m of rope. Density of steel is about 800 kg/m2, and g = 9.81 m/sec2.

    Now there is a question about depth - depth in what medium - air or water? The steel would have some bouyancy in water, but not air.
  4. Aug 17, 2006 #3
    think itis in just air.so how can we use the depth in the calculation??
  5. Aug 17, 2006 #4
    "F(rope) = 100 * F(rod). " the 100 is not the number of rods
  6. Aug 17, 2006 #5
    number of rods is not given and have to find
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