Cellocgw’s argument is the that vehicle with the lesser momentum is more dangerous in a collision, and that lighter vehicle would be safer if heavier. While this can be true, it not necessarily true. Recall definition of momentum: momentum = mass times velocity. Notice that increasing velocity achieves the identical increase in momentum as increasing the mass.
By cellocgw’s argument, any safety improvement that can be had by doubling the weight of the lighter vehicle can also be had by driving twice as fast.
[quote=“bizmail_public, post:22, topic:14399”]
Does that sound right to you?[/quote]
No, because you’ve gotten the transfer of momentum all ballsed up.
Doubling the weight of the target mens it acelerates much more slowly when hit, which means less whiplash and other acceleration induced injuries. That’s why heavier vehicles are - everything else being equalish - safer than lighter vehicles.
I realize we’re on BoingBoing so we both need to oversimplify our arguments, but we owe other readers accurate physics.
Notice the plummeting highway death rates in the developed world over the past 40 years. Did the cars get dramatically heavier? The cars got safer, but not in a way captured in the physics you’ve described thus far.
Momentum transfer between the vehicles is not what determines the degree bodily harm (except in Phys 1). The relevant physical quantity is energy dissipation within each human’s body.
The naive, incomplete physics you presented above do suggest the occupant of the lighter vehicle will sustain great injury. This naive physics is adequate for, say, a '54 Dodge Dart colliding head-on with '57 Cadillac El Dorado at highway speed. The occupants of both cars would probably be dead, but the folks in the Dodge Dart would definitely be dead-er.
In the post that started our discussion, our protagonist was thrown clear. That is, the collision wasn’t inelastic. Thus, your analysis is incomplete. In particular, transforming our protagonist’s experience from a partially elastic collision with fragmentation – a complicated problem to analyze – into an inelastic collision ( by putting him in a comparably sized car) might have led to a worse outcome.
I agree that heavier does genereally mean more momentum transfer to the lighter object, but in the context of modern vehicles heavier does necessarily not mean safer.
America’s highways are more lethal than necessary in no small part because so many do not understand this subtle but vital distinction.
And what, pray tell, is inaccurate about “That’s why heavier vehicles are - everything else being equalish - safer than lighter vehicles.”
The rest of your post I really don’t have an issue with. Well, apart from the patronising tone with which you explain that complex phenomena are (d’uh) complex, and the attempt to split hairs to show what an uber l337 physicist you are. AFAIK, crumple zones and air bags are notably absent from motorcycles, and I have no idea how an example involving two 50 year old cars is supposed to add to anything to this discussion.
Nate Hornby got outrageously lucky. I’m happy for him, he seems like a nice guy, but trying to extend his outrageous luck to a general case is a fools game. Anecdote != data, and population level stats don’t lie. Motorcycles are crapton of fun but dangerous as a form of transport. For lots of reasons, one of which is that they’re going to be on the wrong end of momentum transfer in practically any collision.
To amplify your final point: my recollection of the data is that motorcycle usage on public roads is about ten times more lethal per mile driven than car usage.
Thanks for a great post. I’ll try to improve my tone next time around 8).
Anyway, none of this discussion bears any relevance to the reality that these guys are going flat out at speeds most of us could not comprehend riding, over brutal terrain, for hours. They comprehend the risks of any mistake or unexpected problem better than all of us, but it doesn’t make it any less sad when things go very wrong.
Taylor Robert · 645 followers
5 hours ago via mobile ·
I want to make something very clear and stop the rumors. Kurt Caselli did not crash because of a man made booby trap, a spectator, or any other nonsense that people are saying about his accident. My teammate Ricky Brabec was the fist person to Kurt which was in a very secluded area with no Spectators. Ivan Ramirez showed up shortly after Ricky. They decided Ricky would go get help while Ivan stayed with Kurt. Even though the news didn’t come out until the night time the accident happened while there was still daylight, and didn’t have anything to do with racing at night. This was merely a racing accident and had nothing to do with booby traps, spectators, or another vehicle so please stop spreading rumors
Thank you ensdude850 for shedding some important light on this. I like to think that most reasonable people understand there is a certain window of distorted credibility that comes with today’s lightning spread of information. Unfortunately by the time the truth comes out, it has fallen off the front page.
Now - take all those arguments, and present sample vehicles at proposed speeds with sudden discovery of a deep-but-narrow arroyo in the middle of nowhere. Watch calcs spontaneously burst into flame…
