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Homework Help: What Causes Kinetic Energy To Not Be Conserved

  1. Feb 28, 2008 #1
    [SOLVED] What Causes Kinetic Energy To Not Be Conserved

    1. The problem statement, all variables and given/known data

    In class today we did a lab that dealt with a question about Kinetic Energy. I thought that Kinetic Energy would always be conserved but when we collected our data, that was not the case. According to the data we received, not a single trial we did showed that the Kinetic Energy was conserved. So this brings me up to my question. In the Questions portion of the lab, it is asking the reason as to why the Kinetic Energy isn't conserved if that is what we solved for. What we did was we hit cars together on a frictionless track where they would go in a straight line. We also did a total of 24 trials (12 Elastic crashes and 12 Inelastic Crashes)

    2. Relevant equations

    KEi = KEf + Ff + X?

    3. The attempt at a solution

    What I was thinking is that it has to be friction force that was causing this since not all tracks can be completely frictionless. But even if friction force were to be a part of it, it would have minimal impact on the two colliding objects. When I calculated, the Friction Force number just seemed way to large to be the cause of something like this. I looked on other sites and it says Kinetic Energy can be turned into Heat Energy or other various types of Energies but we haven't learned anything about any other types of energies except for Potential and Kinetic Energy. Is there possibly something I missed? Or is it actually Heat energy that is causing this?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 28, 2008 #2


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    Homework Helper

    If you are sticking the cars together with velcro, that's a huge friction source. That's what it's for. And, yes, the KE it soaks up goes into heat. You don't notice the heat because it takes quite a bit of mechanical energy to create a noticeable amount of heat. Try and create fire by rubbing two sticks together.
  4. Feb 28, 2008 #3

    Oh okay. Yeah they did stick together with velcro. Okay that makes sense then. Thanks so much!
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