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Homework Help: Given 2 Sets of Data, Find 3rd (Velocity, Acceleration?)

  1. Aug 17, 2010 #1
    1. The problem statement, all variables and given/known data
    Falling 20 yards above the ground takes 6 seconds to reach the ground.

    Falling 100 yards above the ground takes 9 seconds to reach the ground.

    How long would it take to reach the ground from 70 yards?

    2. Relevant equations
    v=d/t ?

    I'm completely clueless. Any help with this would be greatly appreciated! Thank you.
  2. jcsd
  3. Aug 17, 2010 #2
    It's best to assume that body is accelerating at [itex]a[/itex] with initial speed [itex]v_{0}[/itex] and height [itex]h_{0}[/itex]. Maybe some assumptions aren't true, but we don't know that before we try to solve the problem.

    So, what you actually have is two equations of the form


    You are given the initial height and the time after which body falls on the ground (to the height [itex]h=0[/itex]). That's all information you need.
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