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Physics Graphs and the Leaving Exam

  • 08-04-2012 10:03pm
    #1
    Darth Frodo
    Registered Users Posts: 72 ✭✭


    Ok, so here's my question.

    If the convention is to put X on the X-axis and Y on the y-axis and calculate slope and multiply it by 2....

    Is it acceptable to put y on the x axis and x on the y axis and then multiply 2 by 1/slope (i.e inverse slope)

    The bedrock of the question is, for let's say graph F against a

    IS IT SET IN STONE THAT F MUST GO ON THE Y-AXIS AND a GO ON THE X-AXIS?

    I mean what i'm doing is mathematically correct but I don't know if the pedantic exam correcter would accept it


Comments

  • #2
    lostatsea
    Registered Users Posts: 320 ✭✭lostatsea


    I think you would probably be OK to do as you describe.

    The convention is the quantity you have control over and therefore the nice numbers go on the x-axis and the quantiy that you measure (and probably not very nice numbers) go on the y-axis. I think this is good practice.

    As you are confident with the Maths and understand what you are doing my advice would be that you stick with the convention.


  • #3
    Chuchoter
    Registered Users, Registered Users 2 Posts: 4,305 ✭✭✭Chuchoter


    Don't chance it, just do it how its meant to be done. I don't think they'd let you away with it as there are marks going for correctly labelled axes and if we did it your way everyone would instantly get that 3 marks.


  • #4
    bscm
    Registered Users, Registered Users 2 Posts: 1,101 ✭✭✭bscm


    Variable goes on the x-axis, function on the y-axis as said before. Convention is y against x (as in: graph a against b, therefore a=y, b=x).

    If it's a straight line through the origin and slope = 1 or -1, then it doesn't matter.

    It does matter if slope does not equal 1 or -1. If you were to graph a=1 b=1, a=2 b=3, a=3 b=5. Graph 1 (a on the x, b on the y) would have a steep slope. Graph 2 (a on the y, b on the x) would have a smaller slope. Therefore you could lose marks if you graphed the values on the wrong axes.


  • #5
    Darth Frodo
    Registered Users Posts: 72 ✭✭Darth Frodo


    Ok, thanks

    There's just one thing, in my mock marking scheme it says to plot delta-theta against I^2 or I^2 against delta theta..... yet for the force and acceleration it's F against a yet they didn't give the 2nd option.

    This seems to imply that only certain ways are acceptable....


  • #6
    bscm
    Registered Users, Registered Users 2 Posts: 1,101 ✭✭✭bscm


    Darth Frodo wrote: »
    Ok, thanks

    There's just one thing, in my mock marking scheme it says to plot delta-theta against I^2 or I^2 against delta theta..... yet for the force and acceleration it's F against a yet they didn't give the 2nd option.

    This seems to imply that only certain ways are acceptable....

    Mocks are shady as it is... the delta-theta and I^2 graph must have had a slope of 1 or -1. Or else you just needed to show a linear/proportional relationship and didn't need to calculate a value from the slope or intercept.

    The force-acceleration graph must have had a different slope and/or you needed to calculate something from the graph.


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