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I need a formula for bouncing balls

  1. Sep 13, 2012 #1
    1. The problem statement, all variables and given/known data
    I dropped a ball from different heights, and got height they bounced up to, but I need a formula for it.

    Data
    Gravity = 9.800 m/s2

    [Initial Height(cm)]----------[Bounced Height(cm)]
    100.0---------------------------81.00
    90.00---------------------------75.00
    80.00---------------------------67.00
    70.00---------------------------59.00
    60.00---------------------------50.00
    50.00---------------------------41.00
    40.00---------------------------34.00
    30.00---------------------------26.00
    20.00---------------------------17.00
    10.00---------------------------9.000
    0-------------------------------0


    2. Relevant equations

    I need a formula that can calculate the bounce height of this


    3. The attempt at a solution

    I calculated the percentage of the bounce height and it averages at about 83% of the height dropped from. Any help would be greatly appreciated
     
  2. jcsd
  3. Sep 13, 2012 #2
    Are you supposed to find an empirical formula for your measurements?
     
  4. Sep 13, 2012 #3
    I'm not sure, my teacher was pretty vague about it. I guess just an equation that you can use to calculate the bouncing of an object
     
  5. Sep 13, 2012 #4
    There is no such equation. An ideal ball in ideal conditions must bounce to exactly the height it was dropped from. But it loses energy because its collision with the ground is not completely elastic and because there is air resistance. Accounting for these losses is a very tricky matter, they depends significantly on the material of ball and its size.

    So I think you should just assume that the ball loses some fixed percentage of energy. And you should find the best fit for the coefficient of the loss from your measurements.
     
  6. Sep 14, 2012 #5
    Try plotting the data on a graph and see what you get. Seeing what is happening visually is a very effective way of examining experimental results. If your graphics package has a curve fitting option, have the package fit a straight line to the data. You will find that the slope of the line represents very accurately the "bounce ratio" (also equal to, the ratio of potential energy from one bounce to the next - see voko comment). It will also agree with the average bounce ratio you determined by averaging the values from all the cases.
     
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