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Re: [Phys-l] Warped 2-metersticks....



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!


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Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
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_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l