During my trip to the US (see post entitled ‘Detroit’, on 21^st August, 2013), my earphones for my IPod broke.  This seems to be a common occurrence, perhaps a case of the planned obsolescence I wrote about on May 1^st, 2013 under the heading ‘Old is Beautiful’.  Nothing very beautiful or repairable about broken earphones, they are just part of our disposable culture.  However, I collect them and use them when teaching engineering students about stress and strain.  Students have all experienced such a failure and so it is an everyday example of engineering that can be used to teach the principles of stress and strain in a familiar context.  A suggested 5E lesson plan for doing this is provided at the bottom of this post.

The lesson plan deals with the stresses in the earphone cable when the ipod is dangled from them and the discussion in class can be extended to include the stresses induced by spinning the earbuds on the end of the cable or the effect of repeated bending of the cable leading to possible fatigue failure (like when you bend your old credit card back and forth to snap it in half).

For more on Everyday Examples in Engineering ‘Bridging Cultures’ on June 12^th, 2013; and ‘Disease of a Modern Age’ on June 26^th, 2013.

5EplanNoS1_uniaxialstrain&ipod