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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

    [tex]h=h_{0}-v_{0}t-\frac{1}{2}at^{2}.[/tex]

    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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