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Kinetic Energy and the Work-Kinetic Energy

  1. Oct 15, 2011 #1
    1. The problem statement, all variables and given/known data
    A 2100-kg pile driver is used to drive a steel I-beam into the ground. The pile driver falls 5.00 m before coming into contact with the top of the beam. Then it drives the beam 12.0 cm farther into the ground as it comes to rest. Using energy considerations, calculate the average force the beam exerts on the pile driver while the pile driver is brought to rest.

    m=2100 kg
    Xi=5.00m
    Xf=12.0 cm =.12m


    2. Relevant equations
    K=.5mV^2
    U=mgh
    F=ma



    3. The attempt at a solution
    I rearranged the formula F=ma to a=F/m. And I tried using a kinematic equation, but I have failed.
     
  2. jcsd
  3. Oct 16, 2011 #2
    I think you want to equate work with potential energy

    F*x = F * (.12m) = mgh = mg(5m + .12m)
     
  4. Oct 16, 2011 #3
    What I did is
    Loss in energy=Loss in PE from the topmost point=mg(5.12)
    Avg. Force=mg(5.12)/0.12
    =8.78x10^5N
     
  5. Oct 16, 2011 #4
    That is the number I get.
     
  6. Oct 16, 2011 #5
    Thank you very much.
     
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