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Homework Help: How to solve this Problem?

  1. Oct 27, 2009 #1
    1. The problem statement, all variables and given/known data
    For safety in climbing, a mountaineer uses a nylon rope that is 50 m long and 1.0 cm in diameter. When supported, a 90 kg climber, sthe rope elongates 1.6m. Find it's Young's modules?

    2. Relevant equations

    F/A= Y * delta L/ Lo -> Y= F*Lo/ A*delta L

    3. The attempt at a solution
    I have Lo= 50m, delta L = (50+1.6)= 51.6m
    m=90kg, g=9.8m/s^2
    So, F= 882N, B

    But I don't have Area, A? Even when I do this -> diameter,d =1 cm= .01m , r= .005m

    So, Area,A= pi r^2 = .0157.

    When I plus in the numbers into the equations, Y= F*Lo/ A*delta L

    the answer comes out to be 1.87*e^7 pa WHILE the real answer is 3.5*e^8 pa. What am I doing wrong?
  2. jcsd
  3. Oct 27, 2009 #2
    Pi * r^2 is much smaller than 0.0157. Also delta L is just 1.6m.
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