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Homework Help: Where does freefall occur?

  1. Oct 5, 2013 #1
    1. The problem statement, all variables and given/known data
    So I am doing my lab, when I realize that I am not sure where the freefall occurs. I collect the data for a ball tossed in the air, and using a vernier motion detector, I found the graphs for displacement, velocity and acceleration (attached). second peak)

    2. Relevant equations

    3. The attempt at a solution
    I figured that the point where the ball was in freefall was when the acceleration graph was between the two maxima points, as marked on the graph, because this is where the only force that acts on the ball is gravity at those points. My partner on the other hand disagreed, and said that it is in freefall from the beginning of the first slope increase to the last slope decrease (at the beginning of the first peak to the end of the second peak (where it returns to become an unchanged acceleration after the ball has landed).
    Which one of us is correct and why?

    Attached Files:

  2. jcsd
  3. Oct 5, 2013 #2


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    The body is in free fall as soon as it is not attached to or resting on anything.
  4. Oct 5, 2013 #3

    Doc Al

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    Staff: Mentor

    It's unclear as to what you are saying. What maxima points on which graph? If you mean the area marked off in grey and with brackets, that's not quite correct.
  5. Oct 5, 2013 #4
    I meant the bottom graph, the acceleration vs. time graph. It is the one that is marked off in grey. Does it mean that its in free fall when the acceleration is 9.81, i.e when the curve of the a/t graph is a constant?
  6. Oct 5, 2013 #5

    Doc Al

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    Staff: Mentor

    The peaks represent the max acceleration when the ball is being launched and stopped--the result of other forces besides gravity.

    Yes, when the acceleration is -9.81 or so.
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