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Help with calculating the range of error accleration

  1. Jun 20, 2009 #1
    1. The problem statement, all variables and given/known data
    Motion on an Incline. I did an experiment where I measured the acceleration of a cart rolling down an inclined plane using 5 different angles and comparing them to those predicted in Newton's 2nd law of motion.

    I am trying to figure out the equation I can use to find the [tex]\Delta[/tex]a using the average deviation in the time as [tex]\Delta[/tex]t. I am treating d (the displacement of the car I used in the experiment) as an exact measurement.

    2. Relevant equations
    I used d = [tex]\frac{1}{2}[/tex]at^2 in a previous experiment and solving for a again would yield me a = [tex]\frac{2d}{t^2}[/tex]. I figured I could use this same derivation to solve for [tex]\Delta[/tex]a which may or may not be my problem.

    I also know by Newton's 2nd law that [tex]\vec{F}[/tex]= m[tex]\bar{a}[/tex] and that that a = g sin[tex]\theta[/tex]

    3. The attempt at a solution

    I tried the range of error for a = [tex]\frac{2d}{t^2}[/tex] coming out with :
    [tex]\Delta[/tex]a = 2[tex]\Delta[/tex]d/[tex]\Delta[/tex]t^2 but this dosn't seem right. Any suggestions would be greatly appreciated. Thanks.
     
  2. jcsd
  3. Jun 20, 2009 #2
    After some more fiddling I came up with a new equation for [tex]\Delta[/tex]a being:

    [tex]\Delta[/tex]a = a([tex]\frac{\Delta d}{d}[/tex] + [tex]\frac{2\Delta t}{t}[/tex])

    Would this be the correct formula?
     
  4. Jun 20, 2009 #3

    Redbelly98

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    Yes, that's right.

    p.s. welcome to Physics Forums.
     
  5. Jun 20, 2009 #4
    Thanks a lot,one more question. When I am doing these graphs it asks me to plot acceleration as a function of mass and another graph of my experimental acceleration as a function of sin. This means that my x axis for both of these should be my acceleration and my y axis the dependent variable of sin or mass in each different graph correct?
     
  6. Jun 20, 2009 #5

    Redbelly98

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    By convention, we usually graph y as a function of x. So a would be along the y-axis in both cases.
     
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