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I use the 2 meter sticks for free fall experiments with electronic timers. I
simply don't worry about the warping. Suppose the overall warp is about 10
degrees - a really extreme case - I don't have any that badly warped. If the
10 degree overall warp corresponds to an average warping of 5 degrees, then
the overall error in measurement will be related to the cosine of 5 degrees
(0.996). This results in a 0.4 percent error in measurement - 8 mm over the
entire length of the stick. Considering all the other errors involved, this
is not worth worrying about. But it is nice to have an answer ready when a
student questions the use of a bent stick.
Bob at PC
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Herb
Gottlieb
Sent: Sunday, March 19, 2006 5:23 PM
To: phys-l@carnot.physics.buffalo.edu
Cc: phys-l@carnot.physics.buffalo.edu
Subject: Re: [Phys-l] Warped 2-metersticks....
It is doubtful that a warped 2-meter stick can provide
accurate readings within half a millimeter even after
it has been carefully straightened out.
A number of years ago The Physics Teacher magazine
reported a comparative evaluation of wooden meter sticks.
I recall seeing a photograph of a stack of these "meter"
sticks that varied in length by as much as 2 or 3 millimeters.
Herb Gottlieb from New York City
(Where it is almost impossible to find a meter stick that is
one meter long.
On Sun, 19 Mar 2006 08:28:05 -0600 Brian Whatcott <betwys1@sbcglobal.net>
writes:
> At 07:31 PM 3/18/2006, Cherie Lehman, you wrote:
> >
> >
> >Hi everyone,
> >
> >I was just wondering if any of the processes suggested for
> "un-warping" the
> >warped 2-meter sticks would disturb the spacing between the
> hashmarks on the
> >sticks. I'd be pretty nervous about turning it into spaghetti for
>
> >fear that I
> >would end up with a French curve. For that matter, would the over
> all length
> >of the stick be changed?
> >
> >Just wondering.
> >Cherie
> >
>
> This is an opportune question for a person interested in measuring
> something
> with an accuracy of less than one half the smallest division mark
> over the
> length of the rule (which would be the rational lower limit of
> acceptable
> accuracy in a measuring stick). It is however, the sort of
> question
> only likely
> to be answered by someone in a physics lab or class-room.
> Other wood users can be content with slightly wider acceptable
> tolerances.
> The cheapest one meter sticks I've seen go under $2. A suitable
>
> experimental
> prospect, possibly?
>
>
> Brian Whatcott Altus OK Eureka!
>
>
> _______________________________________________
> Forum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
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>
>
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