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Teachers' Lounge Discussion: Practical application for algebra

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From: David Andrzejewski <david@dpgf.org>
To: Teacher2Teacher Public Discussion
Date: 2004030720:34:04
Subject: Re: mathematics

I used to work in the biomechanics industry, which is related to
ergonomics (the science of finding the most compatible work
environment).  There's this lifting equation called the NIOSH lifting
equation.  It is rather complex, but here's a simplified version: 
FORCE = constant*lever arm*weight of the load.
You can do your own research on the NIOSH eqn, but the gist is the
"old" debate as to why you should lift with your legs instead of your
back.  If one is picking up a box (legs straight, bent almost parallel
to the ground at the waist) how does the compression on L5-S1 (the
vertebrae that bend near the waist) to picking up a box with knees
bent, and straddling the load.  It turns out that the lever arm when
you are lifting with your back is much greater than the lever arm when
lifting with your knees(lever arm refers to the distance the load is
 from the fulcrum).  Therefore the compression on L5-S1 is much greater
(by a factor of the ratios of the lever arms).  
You can also use this example when teaching inverse/direct variation. 
Hope this helps a little.

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