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Homework Help: Hooke's Law to find work.

  1. Nov 11, 2009 #1
    1. The problem statement, all variables and given/known data
    It takes 3.23 J of work to stretch a Hooke's-law spring 12.1 cm from its unstressed length. How much extra work is required to stretch it an additional 5.76cm. Answer in Joules.

    2. Relevant equations
    F= -kx
    W= FD

    3. The attempt at a solution
    At first, I try using proportions to do this problem:

    3.23/12.1 = x/5.76
    I got that answer but it was wrong.

    So I tries finding the force using w=fd. Then I multiplied that by 5.76 and I got the same answer as doing it the proportion method.

    What am I doing wrong. Do I need K or do I need to use the equation W = 1/2kx^2? Thanks in advance.
  2. jcsd
  3. Nov 11, 2009 #2
    Oh figured it out, nvm.
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