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Homework Help: Projectile HELP

  1. Sep 27, 2010 #1
    Projectile HELP!!!

    1. The problem statement, all variables and given/known data
    Bill kicks a rock off the top of his apartment
    building. It strikes a window across the street
    14 m away.
    The acceleration of gravity is 9.8 m/s
    If the window is 16 m below the position
    where Bill contacted the rock, how long was
    it in the air?
    Answer in units of s.
    How fast was it moving when it left Bill’s
    Answer in units of m/s.
    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 27, 2010 #2
    Re: Projectile HELP!!!

    (delta)y = v0t - 1/2gt^2

    just plug in the numbers
  4. Sep 27, 2010 #3
    Re: Projectile HELP!!!

    >>just plug in the numbers

    but thats not how you understand the physics of the problem.

    Think about the question at hand and try to figure what is actually going on.

    [PLAIN]http://img237.imageshack.us/img237/641/blockfc.png [Broken]

    V initial has only a horizontal component which equals its total magnitude.

    Your knowns:

    1) The final height
    2) The total distance traveled
    3) And Gravity

    Know you must solve for time, which equation lets you solve for t by only knowing position and acceleration?

    Know you must solve for V initial, what equation do you think you should use for this? (The derivative of position is velocity)
    Last edited by a moderator: May 4, 2017
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