Bike and Motorcycle Helmets HOME History     Motorcycle helmets were the  invented before bike helmets believe it or not; they came about after the death of T.E. Lawrence (Lawrence of Arabia) who had died in a motorcycle crash that had given him a traumatic head injury. At first, helmets were ineffective, but after decades of research and progression in materials technology, we today have helmets that protect cyclists and motorcycle riders from some of the worst crashes.   Early Motorcycle helmet Image source-http://4.bp.blogspot.com/-AxyyyIR0jN0/UV6szsyPpNI/AAAAAAAAHCs/ORKEbomzN9Y/s1600/motorcycle-race.jpg The Physics Both bike and motorcycle helmets are typically composed of a hard outer shell and a soft inner shell. The hard outer shell is usually made form a light material like plastic or carbon fiber. This layer takes the brunt of the impact and spreads it over a broader area so its not just directed in one small area where the force would over come the materials strength. Then there is a soft inner shell that is made of a Styrofoam like material. This inner layer is designed to compress and absorb force as well as slowing the time it take for your head to actually impact, which in turn reduces the force you feel/take and makes traumatic injury less likely.     So in a hypothetical scenario your going down a big hill on your bike and hit a tiny rock. You fly off your bike, your head hits the ground, the hard plastic absorbs some of the force as well as spreading it out your head then impacts the inner foam layer and compresses it, which increases your head impact time and protects you. Your able to get up with a minor headache and ride home for supper and pretend it never happened.          Bike Helmet as you can see there is a foam layer covered by a harder plastic layer. Image source-https://www.bikerumor.com/wp-content/uploads/2010/07/lazer-oasiz-mountain-bike-helmet-brian-lopes08.jpg Motorcycle Helmet Same story with this helmet, although it was designed for a different vehicle the principle and constriction are still the same. Image source-http://www.whitedogbikes.com/images/blog-img/nitropanther/ngfp-halffull-600x478.jpg