# Calculations about Bicycle Helmets (1 Viewer)

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#### kittyNoel

I am doing a report on Bicycle Helmets and it's supposed to include calculations of some kind but as I am looking around and writing about it i'm not too sure what would be the best kinds of calculations to put into this that wont sound out of place. The report needs to tell about how it protects us from harm in an accident and connect it's intended uses to the units I have been working on (which are energy, harmonic motion, momentum, and gravitational fields).
I have found out that there is foam in the helmet that will crunch under force is this something I could work with? Where would be the best place to start?

#### berkeman

Mentor
I am doing a report on Bicycle Helmets and it's supposed to include calculations of some kind but as I am looking around and writing about it i'm not too sure what would be the best kinds of calculations to put into this that wont sound out of place. The report needs to tell about how it protects us from harm in an accident and connect it's intended uses to the units I have been working on (which are energy, harmonic motion, momentum, and gravitational fields).
I have found out that there is foam in the helmet that will crunch under force is this something I could work with? Where would be the best place to start?

I googled bicycle helmet testing tutorial, and got some good hits. The first one on the list looks to be the definitive source of information. You are correct that force and momentum come into play. Also look into the term "impulse" -- that should also be part of the calculations.

http://www.bhsi.org/

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#### kittyNoel

Ya I have looked at that site its got some good information but I didn't see any real calculation's thanks for having a look on Google for me though.

#### berkeman

Mentor
Ya I have looked at that site its got some good information but I didn't see any real calculation's thanks for having a look on Google for me though.
Well, they at least show impact energy graphs for good helmets versus no/bad helmets. That's pretty quantitative. And the links in this paragraph from the site seem to be good ones to follow:

http://www.bhsi.org/general.htm

A typical standard specifies impact tests, strap tests, characteristics of materials to be used, required coverage, labeling and other requirements. Some have tests to simulate low temperature performance, hot performance, wet performance and sunlight ageing. Test equipment is described as well as the severity of the testing. For a look at a complete helmet standard, check out the Snell Memorial Foundation site, where their standards are all available. Or you can read the US CPSC bicycle helmet standard, probably the most-used standard in the world. For a look at a point-by-point comparison of bicycle helmet standards, check out our short comparison or our more detailed long comparison.
Have you followed those links, or re-googled with my search terms to see what other pages are available?

#### kittyNoel

i've looked around there site a far bit, I'm looking into impulse now and trying to think of a way to connect it all with numbers. I looked at a bunch of stuff on the standards and I am still not really sure what to say exactly as showing some calculations...

#### berkeman

Mentor
i've looked around there site a far bit, I'm looking into impulse now and trying to think of a way to connect it all with numbers. I looked at a bunch of stuff on the standards and I am still not really sure what to say exactly as showing some calculations...
Also google energy absorbing foam calculations...

#### kittyNoel

Does this make sense?

The impulse of your head hiting the ground without a helmit would be
J = mass of head * intial velocity - mass of head * final velocity
the final velocity in this case would be 0 since it just comes to an abrupt stop.

Where as if you place a helmet inbetween on your head first you have:
J = mass of head * intial velocity - mass of head * final velocity
but the final velocity will be less because the helmit slowed you down.

If that works where would I find any kind of numbers to put into this?
I tried to look up energy absorbing foam calculations but I can't find anything that I understand.

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