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Homework Help: Newbie needs basic help with magnitude slope

  1. Nov 29, 2012 #1
    1. The problem statement, all variables and given/known data

    I have done an experiment where every 10 seconds I had to say my instantaneous speed while drivng a car and my co-passenger would record the time (we carried this out over 20 minutes). I then plotted this out on a graph with time (s) on the X axis and km/h on the Y axis.

    I now need to calculate the magnitude of the maximum slope and then make a comparison statement about my result vs. the rate of acceleration due to gravity. ....and to be honest this is all new to me and I'm not sure if I'm doing this right.

    2. Relevant equations

    This is what I went with

    y1= 0km/h, y2=50km/h, x1= 0s, x2= 10s. I then used rise over run (y2-y1)/(x2-x1)
    but I'm not sure if this is the right formula or what you'd call the resulting units...km/h or maybe convert to m/s or m/s^2 ? and I'm not sure what it represents ? Acceleration (change of velocity/ time)??

    3. The attempt at a solution

    50-0/10-0 = 5 (somethings) ...then I thought maybe 50km/h should be put into m/s which I came up with 13.88 m/s....meaning (13.88 m/s) /( 10s) = 1.38 m/s or maybe it should be 1.38 ms^2.

    so when i then compare this to the acceleration rate due to gravity (9.8m/s^2). I will make a statement my acceleration rate is less than that of gravity.

    Any help anyone is willing to offer wold be most appreciated.

  2. jcsd
  3. Nov 29, 2012 #2


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    Yes, acceleration. It's useful to keep track of units by keeping them in the equations:
    50km/h / 10s = 5 km/h/s = 5000 m/h/s = 5000/3600 m/s2
    My guess is that you are expected to say how many g's it is.
  4. Nov 29, 2012 #3
    cool, thanks for the help. We haven't touched on g's yet....(I don't think) . We are at are 101 stage for those with little or no background,so I imagine the g's may be not be too far off.
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