It is all about the angular momentum of the cyclist wrt to the road.
I'm used to motor cyclists wearing leathers. Bare skin in an accident looks terrifyingly abrasive.
Nobody's ever managed to make it more that a second.
http://i.imgur.com/gRqg50J.png
at about 22mph. ;)
That's pretty much what happened to me. I was going walking speed on a bike, popped a wheelie, handle bars came off, I tumbled forward and landed collar bone first onto a curb. Hairline fracture at about age 14.
I pulled the brake lever on my road bike once, and it FELL OFF. Went right into the front spokes and launched me over the handlebars like a cannonball. It was like putting a metal rod right into the front spokes.
That sounds very concerning. I didn't know that could even happen...
I don't know too much about bikes, but the one I had used some type of bolt to connect the handlebars to the main frame.
I was adjusting the height of the handlebars and I guess I didn't tighten it enough in the end. User error in all its glory.
1: spherical cow/fermi estimate
You can probably produce more power approximated by the volume of the muscle though.
This never made any sense to me. Muscles are made up of groups of fibers, which are made up of chains of sarcomeres. How could strength be proportional to cross sectional area rather than volume of the muscle?
The same reason that's true of strength of passive members; the limiting factor is the force that will cause shearing, which is basically the strength of one bond in the lengthwise direction times the number of them supporting in parallel in the cross section. So, given the same material, cross sectional area determines strength.
The entire line of reasoning seems to rest on the idea that the smallest unit we consider runs from one end all the way to the other.
It doesn't really matter, except the not being homogenous end-to-end means it's the weakest point that matters. But, irrespective of the structural details, there is some force in the direction of contraction that will cause failure, and that force is proportional to, basically, the number of linkages it is distributed across in parallel (not connections in series, such as along the chain) which is proportional to cross-sectional area.
> The entire line of reasoning seems to rest on the idea that the smallest unit we consider runs from one end all the way to the other.
It is not (in fact, the entire reason it is true of any material is because even structures which seem to be end to end are composed of smaller structures with fallible linkages; if there were indivisible end-to-end structures, this would cease to be a concern.)
Although I was basing that on force exerted by gravity (which is proportional to mass), whereas deceleration might be spread out proportional to length, so it might work out to L² anyway. It's too late to edit though.
Or is this a myth?
I looked up the stats going back a few decades - in the sixties, an average hundred kids died in traffic each year here in Norway. Now? Two or three. Yet we drive more and the population is significantly larger, too.
Drowning (the other biggie) is down by a similar factor.
Generic accidents? Also down by at least an order of magnitude.
We may sigh all we want that kids today are glued to their playstations while we were out building tree huts, conducting -ahem- applied pyrotechnics experiments and similar - but the fact of the matter is that kids today survive childhood. We didn't. :/
The main difference is being supervised by a reasonable adult or not and how streets near homes have changed.
Kids can only be left to free roam in a very safe environment - and even that is not entirely without risks. Alternatively only kids who are shown to be reasonable can do that - it takes parental sensitivity.