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Acceleration in free fall: find final velocity and height

  1. Sep 7, 2009 #1
    1. The problem statement, all variables and given/known data
    A student drops a ball from the top of a tall building; it takes 2.5 s for the ball to reach the ground.

    A.What was the ball’s speed just before hitting the ground?
    B.What is the height of the building?


    2. Relevant equations
    v=V(not) + at

    x=V(not)t + 1/2at(Squared)

    V(Squared) =V(not) + 2ax




    3. The attempt at a solution

    I wrote the following

    V(not) = ?
    a= 9.80 (Because it is a free fall question?)
    t= 2.5
    v= ?
    x= ?

    I think I am missing a variable but I do not know which one.

    thanks


    EDIT: Will I have to do A2+B2=C2?

    If so what will be the legs and what will be the hyp?
     
  2. jcsd
  3. Sep 7, 2009 #2
    Re: Acceleration

    x=V(not)t + 1/2at(Squared)

    There is only one unknown in this equation.

    and this v=V(not) + at
     
  4. Sep 7, 2009 #3
    Re: Acceleration

    How do I figure out the other varibles
    I have a and t only how do I figure out the 3rd one?
     
  5. Sep 7, 2009 #4
    Re: Acceleration

    Vo or V(not) is your initial velocity. In the problem it says that the student drops the ball, what does that mean according to the initial velocity?
     
  6. Sep 7, 2009 #5
    Re: Acceleration

    I got it
    I got it
    I got it
    I got it
    I got it



    Yeah!

    Thanks for your help man!
     
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