Originally Posted by
TMonk
Well my question for you is how much force did it take to ruin (completely crack) that helmet?
That would have been that much more force on my noggin.
Im not gonna go through the motions of calculating that force but to me it seems like it would be a significant relative to the net force that my noggin experienced, atleast within an order of magnitude.
Can you give me some numbers? Because if not than your claim is just as ignorant as mine.
Also the distance component of this particular application of force is very minimal, so it is best quantified as a point force. As we all know, W(energy)=FxD and the D in that equation is slim to nill so it is better to think about force.
I've already posted the numbers, countless times.
A bike helmet is only designed to absorb the energy of a fall over type impact: any additional energy is going to be transmitted to the head. If you aren't moving and just fall over, your head will hit the ground at roughly 12mph, with about 1300 joules of energy. If your head is going 30mph when it hits the ground/car/whatever, that's about 6150 joules. The helmet will potentially subtract its 1300, leaving you with a 4850 joule impact. That's the same as from a helmetless 27mph impact.
Does anyone ever post, "i'd have been dead if I was going 30 mph but luckily I was only going 27."? No. But they always say they'd be dead if they didn't have a helmet. But all that helmet is doing for you is that very modest 1300 joule savings, which is equivalent to a few mph slower impact.