Jumat, 21 Maret 2014

Choose only one of the following helmet types to research:?

Q. Choose only one of the following helmet types to research:
⢠bicycle
⢠space suit
⢠motorcycle
Report on your work in a well-organized and well-written
report. Your report must include relevant sample calculations
and examples; a thorough discussion of the principles of physics
described in this unit; and appropriate diagrams and notations to
demonstrate your understanding of the relationship between the
design of the helmet and its use.
Thanks in advance!


Answer
go for motorcycle helmets as there is lots of info on how they are made & testing +the bs , ce , snell. eu, standards & lots of others,

How do bicycle helmets work?




Forgetful


There is a "shell" and a "liner" in a bicycle helmet, right? what is the purpose of those things? Is the shell supposed to stop it from breaking or is the liner supposed to be crushed?
Simple language please.
thanks!!!!!



Answer
There are variations depending upon the quality of the helmet and the purpose... for example, some DH helmets are practically MX helmets now but, in general...

Bike helmets have the liner and shell as you've mentioned, the liner actually does the majority of work in saving you from a fall. The shell is really just there to prevent things like stick and such on the tral from penetrating the liner and stabbing you in the head, or to keep the liner from coming apart on hard impacts. The liner is what handles the energy transfer that prevents you from sustaining severe injury. When you take an impact, the liner is supposed to get crushed... in doing so, it converts the kinetic energy (the energy of an object in motion) of the impact into thermal energy (heat) as the liner is crushed. Remember, energy can never be created or destroyed, it can only change forms... The type of material used in the liner and the overall quality of the helmet determine just how effective it is but that's the basic principle in ALL helmets actually. Most common helmets use an EPS liner, Expanded PolyStyrine, and are good for just one serious impact... Once the liner has been crushed, it no longer has the capacity to be crushed much further to allow for the conversion of energy needed to protect your head. Some other helmets use materials that allow the energy conversion to take place repeatedly and only need to be replaced if the shell material is compromised... these are typically MX helmets or very high-end downhill helmets.

Also, it's worth noting that essentially all bike helmets pass the same certifications so there isnt a whole lot of difference in protection between a $40 helmet and a $140 helmet... Most of the extra money that you pay goes into what was spent on R&D to figure out a way to incorporate more vents into the helmet without lessening the protection offered.




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