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Homework Help: Supermans initial velocity?

  1. Oct 19, 2011 #1
    1. The problem statement, all variables and given/known data
    A student is determined to test the law of gravity for himself. He steps off a skyscraper 320m high, stopwatch in hand, and starts his free fall. Five seconds later, superman arrives at the scene and dives off the roof to save the student. What must superman's initial velocity be in order to catch the student just before the student reaches the ground? Assume superman obeys the laws of physics like any other free falling objects

    2. Relevant equations

    v2^2 = v1^2+2aΔd

    3. The attempt at a solution
    I used the formula above to calculate that the student will be travelling at 79m/s just before he hits the ground. But i think i have the wrong approach
  2. jcsd
  3. Oct 20, 2011 #2


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    Homework Helper

    That is the correct speed for the student - or very close; depends what value for g you used.
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