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Homework Help: Freely falling bodies

  1. Jun 9, 2007 #1
    1. The problem statement, all variables and given/known data

    A ball is dropped from rest from the top of a cliff that is 24 m high. From ground level a second ball is thrown straight up at the same instand theat the first ball is fropped. The initial speed of the second ball is the same as that with which the fist ball hits the ground. In absense of air resistance, the motions of the balls are just the revers of eachother. How far below the cliff do the balls cross paths?

    2. Relevant equations kinematic equations involving vi, vf, a, x and y and time.

    3. The attempt at a solution
    I know it takes 2.21 s to fall 24 m, and for ball 2 to reach vi of ball one. Vf1 = vi2= 21.7 m/s

  2. jcsd
  3. Jun 9, 2007 #2

    Doc Al

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    Staff: Mentor

    So far, so good. Now write expressions for the position of each ball as a function of time. (Make sure you measure the position from the same point for each.) Then you can solve for where the paths intersect.
  4. Jun 9, 2007 #3
    Sorry, you've completely lost me....I keep getting 24 m with what I'm trying...any other thoughts?
  5. Jun 9, 2007 #4


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    Homework Helper

    Can you show what you're doing?
  6. Jun 10, 2007 #5
    write the distances travelled by each as a function of time
    then add them and equate to the hight of the cliff

    does this help? or do u need more?
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