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Homework Help: Physics problem, basketball dunk (Hookes law)

  1. Apr 3, 2013 #1
    1. The problem statement, all variables and given/known data
    A 95kg basketball player slam dunks a basketball and hangs onto the rim. Find out how much the rim bends if its spring constant = 7400 N/m and the basketball rim is 2 m in the air.

    2. Relevant equations
    Ep = 0.5 k x^2
    Ek = 0.5 m v^2
    Eg = mgh

    3. The attempt at a solution
    The book got 0.15 m. My answer is way off, what did I do wrong? I think this should be right.

    Ep1 + Ek1 + Eg1 = Ep2 + Ek2 + Eg2
    Ep1 = 0, Ek1 = 0, Ek2 = 0

    Eg1 = Ep2 + Eg2
    mgh = (1/2)kx^2 + mg(2m - x)

    1862 J = 3700x^2 N/m + 1862 J - 931x N

    3700x^2 N/m - 931x N = 0

    931x N( 3.97x / m - 1 ) = 0

    x = 0 or 3.97x/m = 1

    x = 1/(3.97/m) = 0.25 m.

    Book got 0.15. My answer is way off and I'm not sure why it could be look this. Is my logic correct? Am I correct?
    Last edited: Apr 3, 2013
  2. jcsd
  3. Apr 3, 2013 #2


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    Homework Helper
    Gold Member

    It is not entirely clear, but I don't think it is asking the maximum extent of the bend under SHM. It's a statics question: if the player hangs on for an arbitrarily long time, what will the extent of the bend settle out at?
  4. Apr 3, 2013 #3


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    Science Advisor

    You are not given any speeds so there is no point in looking at kinetic energy. The problem is just "if a 95 kg object is hung from a spring with spring constant 7400 N/m, how far will the spring extend?"

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