Re: Graphing d vs t

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 10:23 -0400 11/12/01, Tim O'Donnell wrote:
> While at the NSTA conference in Columbus, on Friday at
> one session one teacher was adamant about when
> graphing distance vs time, time was ALWAYS on the
> horizontal axis.  I thought it depended upon what was
> being controlled. If I control time and measure distance,
> then time is on the horizontal axis but if I control
> distance and measure time than distance should be on
> the horizontal axis. Any thoughts?
I don't think we should get all het up about which axis is which in
these things. We should put the variables on whichever axis turns out
to be more useful. Since the usual thing you want from a d vs. t
graph is a slope that gives velocity, it makes sense to put time on
the horizontal axis. But in relativity and Feynman diagrams we
routinely put time on the vertical axis, because we are looking for
something other than the slope.

Students learn in middle school, and sometimes in their math classes
that there is something magic about always putting the "dependent
variable" on the vertical axis and the "independent variable" on the
horizontal. But often which variable is dependent and which is
independent is a function of which is easier to measure and which is
easier to choose, not any sort of causal reason. So I would say that
how you orient the graph depends on what use you intend to make of
it, rather than which variable is dependent and which is independent.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

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