Re: The air track experiment

[Bob Sciamanda <trebor@VELOCITY.NET>]

Hi Jack,
I am intrigued by your post cuz I follow everything but your conclusion.
I agree that if the acceleration goes as t to the power b, then it follows
that v goes as t to the power (b+1) and x goes as t to the power (b+2).
 From this it follows that x(v) goes as v to the power (b+2)/(b+1) = 1 +
1/(b+1).

So what?  Where's the conundrum?  I don't get the point!

_Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: JACK L. URETSKY (C)1998; HEP DIVISION, ARGONNE NATIONAL LAB ARGONNE,
IL 60439 <JLU@HEP.ANL.GOV>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, August 24, 1999 12:35 AM
Subject: The air track experiment


>         This experiment, as I have seen it, involves a sliding mass on
an
> inclined air track.  The mass is released from rest and slides a fixed
and
> measured distance through a velocity measuring device.  The distance
from
> the point of release to the velocity measuring device is varied so that
one
> measures the variation of distance traveled vs velocity.  The
instructions
> state the expected functional relationship between the two quanitities,
so
> the student is invited to measure the (constant) value of the
acceleration and
> , with some trig, the value of g.  Truly, a mind-numbing exercise.
>         I suggest the following variation on this experiment.  If the
acceleration
> were a power, say a, of the time of travel, then the distance traveled
would
> vary as a power 1 + 1/(a+1) of the final velocity of the mass.  Now for
those
> who would yell YOU'RE WRONG! to those who would propose that a is
different
> from zero, I invite you to determine limits on a from a real experiment.
I
> suggest, therefore, that instead of using this experiment to determine
the
> constant g, the experiment be used to determine acceptable ranges of a.
I
> think that I can guarantee that a=0 is not an assured outcome.
>         P.S.  I once tried, in a lab, to duplicate the Galileo inclined
plane
> experiments.  All the inclined planes I could find were badly warped,
and the
> results varied widely from the expected.  It is my private opinion that
Galileo
> "cooked" his results - go for it, inquisition!  Well, Newton was caught
cooking
> too, therby demonstrating the power of abstraction from uncertain
experimental
> results.
>                                         Regards,
>                                                 Jack
>
> "These several facts prove nothing, for one cannot deduce a principle
from so
> few examples, but they do at least indicate that the ability to learn to
spell
> correctly is a gift; that it is born in a person, and that it is a sign
of
> intellectual inferiority.  By parity of reasoning, its absence is a sign
of
> great mental power."
>                 Mark Twain, "Extract from Eve's Diary'.