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Homework Help: Work against spring force

  1. Nov 9, 2004 #1
    so i have tried this problem fifty million times and i can't get the right answer. hopefully someone can help. when a 75 g mass is suspended from a vertical spring, the spring is stretched from a length of 4.0 cm to a length of 7.0 cm. If the mass is then pulled downward an additional 10 cm, what is the total work done against the spring force in joules? i converted grams to kilograms and cm to m and used the equation f=kx and then plugged those numbers into w=1/2kx^2. i can't get the correct answer of 0.21 J. please help
     
  2. jcsd
  3. Nov 9, 2004 #2
    unfortunately, i get 0.1962 J; a wrong one .
     
  4. Nov 10, 2004 #3

    Kurdt

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    i get the correct answer of 0.21J

    k=24.5
    x=0.13

    plug them in and out pops the answer
     
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