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The Bouncing Ball Lab- Loss of Energy

  1. Sep 15, 2014 #1
    1. Okay. So, my lab is to bounce a ball at a given high while i calculate the time, mass, and different heights. Given these I find the PE, Velocity, and Difference in PE. I've gotten most of the lab complete but there is a final question that asks "If you wanted the golf ball to rebound to a height of 3ft, which was the tested initial height, how high in units of ft would the golf ball need to be initially placed before released.
    2. There is also a question that asks: "Calculate the difference in PE in J between the initial height and rebound height, and explain what happened to account for the loss of height in terms of conservation of energy?" I understand how to find the difference the PE from the initial height and the PE after it was rebounded but what does she mean by the conservation of energy thing?

    3. For the golf ball I have an initial height of .91m, a PE of .4 J, a velocity of 2.33 m/s, avg rebound height of .56m w/ a PE of .25 J, and the difference is .15 J.

    4. Im not sure where to start, really. I thought of possibly doing .4J/.25J and plugging that into PE=mgH but I'm not sure if that'd give me the answer. If anyone could please help me that'd be great. This paper is due at 8am tomorrow morning. Thanks!
    Additional info: M=45g Initial height 1 yd travel time: .39sec.
  2. jcsd
  3. Sep 15, 2014 #2


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    8am in which time zone? ;)

    You cannot use a ratio as an energy value.
    You can assume that this ratio is the same for each bounce (it won't be, but it is a good approximation). What was the fraction of energy lost you observed? If it is the same for every bounce, ...

    Did you hear of conservation of energy? You start with .4J and end up with .25J, could this be an issue?
  4. Sep 15, 2014 #3
    Sorry, Eastern Time Zone. Clemson, SC. Well what i did was (.045kg)(9.8m/s^s)(.91)=.40 kgm^s/s^s=.40J Then, (.045kg)(9.8m/s^2)(.56m)= .25J. So, .40J-.25J= .15J. And, i understand that the energy lost will not be the same, as the heights will be different with every bounce due to the loss of energy. I just can't seem to figure out the initial height. Any hints you can give me? I'm really stuck..
  5. Sep 16, 2014 #4


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    All of my previous post is a collection of hints how to proceed...
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