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Homework Help: Newton's 2nd Law Lab

  1. Sep 26, 2012 #1
    1. The problem statement, all variables and given/known data

    We did a lab in class where we had a cart and we had nothing on top of it. We added different forces at the end of a pulley to see how the acceleration differed with different forces. One of the questions on our lab was: We tried to keep the "mass constant". Why is this really not true? Does this affect our results significantly? How could this be resolved?

    2. Relevant equations
    a=f/m


    3. The attempt at a solution
    I can't think of any way that the mass would not be constant. Its not like we were leaning on the cart or anything.

    Thank you!
     
  2. jcsd
  3. Sep 26, 2012 #2

    PeterO

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    Homework Helper

    How were you "generating" the force? If you were hanging the masses on a string over the pulley - then those masses were also accelerating; changing the over all mass being accelerated.

    For example, if you drop a 1 kg cart, it will begin to accelerate at g, like anything else you drop.

    If you hang a 2kg mass on a string over a pulley, you might think it generates a force twice the weight of the 1 kg cart. That could lead you to expect an acceleration of 2g. Will that 2g acceleration really happen?
     
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