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Homework Help: Free-fall problem

  1. Sep 13, 2012 #1
    1. The problem statement, all variables and given/known data
    A ball thrown up falls back down in front of a window from where an observer sees the ball for a total of 0.5 seconds. The window is 2 m. tall. What is the maximum height of the ball?

    2. Relevant equations
    1D Kinematic equations

    3. The attempt at a solution

    I got that initial velocity from the bottom of the window by using [tex]V^2 = V_0^2 + 2a(x - x_0)[/tex].

    I set the seconds to 0.25 since 0.5 is the total, and -9.8 for the acceleration of gravity.

    Then I plugged all of that back into [tex]V^2 = V_0^2 + 2a(x - x_0)[/tex] by setting V^2 = 0 because the velocity at the highest point is 0, V_0 is the previously found initial velocity, accleration is -9.8 again, and x - x_0 is the unknown. I got 1.88 m., which is obviously wrong because the window itself is 2m. But I guess it could be the answer, but I'm not sure. It doesn't look right.
  2. jcsd
  3. Sep 13, 2012 #2
    How did you get the initial velocity from this?
  4. Sep 13, 2012 #3
    Take maximum height as the starting point where the ball being dropped.
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