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Work-Kinetic Energy Theorem

  1. Jan 9, 2016 #1
    1. The problem statement, all variables and given/known data
    A high diver(m = 62kg) walks off a platform 15 meters above the water below (assume velocity inital = 0). The diver reaches a depth of 2.2 metres in the pool before coming to a stop.
    1. What is the diver's change in kinetic energy (Answer: -9114J)
    2. What is the average force of the water pushing up on her? (Answer: 4750 N ... the acceleration corresponds to a about 8 g's)

    I don't get the correct answer to the first question and I don' know how to attempt the second question. Please help and please show me the steps.
    2. Relevant equations
    Work Energy Theorem

    3. The attempt at a solution
    1. Change in GPE = Change in KE
    mgh = change in KE
    (62kg)(9.8)(17.2m(
    change in KE = 10450.72, which is the wrong answer.
     
  2. jcsd
  3. Jan 9, 2016 #2

    Doc Al

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    Staff: Mentor

    I presume they want the change in KE once she hits the water. So what is her KE when she hits the water?
     
  4. Jan 9, 2016 #3
    The KE when she hits the water is 9114J
     
  5. Jan 9, 2016 #4

    Doc Al

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    Staff: Mentor

    There you go. So you can answer part 1 now, correct?
     
  6. Jan 9, 2016 #5
    How do I sart part 2
     
  7. Jan 9, 2016 #6
    Sorry, How do I start part 2
     
  8. Jan 9, 2016 #7

    Doc Al

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    Staff: Mentor

    By applying the work energy theorem.

    Remember, you are trying to find the average force that the water exerts. What other force acts?
     
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