This is a way to determine the Young Modulus as an individual, rather than group practical. For years I thought that you needed a pulley for the wire, but it turns out you don’t. Without that limiting factor, it becomes a pfaff reducing exercise.
Get a plank of “whatever you can find” width, about 1.2m long, drive a screw in about 5cm from one end. Photocopy a normal ruler at 100% then at 90%. Check the reduction is accurate! Use the 90% to make a vernier scale. Get about 2m of 32swg copper wire and tape the vernier scale to the wire at 1m from the nail. Line the vernier up with the 100% scale and gently hang 1N weights to the end of the wire that hangs off the end of the plank, measuring each extension. The diameter of the wire is done traditionally by using a micrometer or looking up the diameter of swg wire in mm.
Steps and Photos
For those of you who assess against CPAC, this is a good experiment for 3a (Identifying Risks) and 3b (Working Safely). I use the Hazard | Risk | Control approach to a risk assessment. e.g.
Flailing wire causing damage to exposed skin/eyes. Weight falling on feet.
Eye protection. Weights over wire for kinetic energy transfer. Sandbag on floor.
I realise that the weights on foot issue is not a massive one, and using copper wire makes the flailing wire unlikely too, but they do need practise thinking about these things for bigger challenges ahead.
Three graphs of real data showing how the pulley (middle) makes no difference, the first and third are with the wire simply hanging over the edge of the plank. The final one (green dots) is Hooke’s Law.
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