MadSci Network: Physics

Re: How does the weight/size of a rubber band affect its elasticity?

Date: Tue Mar 29 03:15:25 2005
Posted By: Ed Stammel, Faculty, Computer, SUNY Delhi
Area of science: Physics
ID: 1110056806.Ph


As an experiment I attempted to duplicate Hooke’s law in a Physics class 
with rubber bands.  We got a huge surprise.  We hung rubber bands of 
various sizes over a support, attached a plastic pail, and began to fill 
it with sand.  At first the band appeared to follow the expected pattern.  
With increased sand and the resulting force the band elongated.  But; as 
we approached the elastic limit, it not only stopped lengthening it 
sometimes actually contracted!  It was almost as if the band tried to 
resist breaking.  Of course it can not.  So what was happening?

We don’t really know.  After trying a number of different bands we found 
that brand, age, thickness, length, method of attachment, and rate of 
increasing force all influenced the elastic limit.  But no matter what we 
did they all underwent the “resist breaking” phenomenon.  

I recommend you do this outdoors with water on a warm day.  That way you 
can estimate the mass by keeping track of the volume since one Liter is 
about one Kilogram which is around 9.8 Newton.  Maybe you can discover 
some kind of relationship…we never did find a reliable predictor of 

By the way…get ready to get wet!

Have Fun,

Ed Stammel

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