>>is that the equivalent of a 70MPH impact into a stationary object?
I used to think so, unquestioningly, it's the commonly held view, but now, I don't think it's true.
Yes, there's twice the energy, but, there is also twice the crumple zone in which to dissipate the energy.
Consider it another way. Imagine watching a high speed movie of 2 cars crashing - but, the 2 cars are exact mirror images of each other, and perfectly aligned with each other. The common impact surface will not move - therefore it would have made no difference had the impact being into a solid concrete block.
Phrased another way, impact tests into a solid concrete block are actually a good approximation to simulating crashing into a mirror image of yourself coming the other way.
Edited by Number_Cruncher on 09/05/2009 at 21:23
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Guys, come on...
Energy = 1/2 x Mass x (velocity squared).
Doubling the speed quadruples the energy.
35mph into 35mph is NOT the same as 70mph into zero.
I think 5th gear did a test perhaps 5 yrs ago with a variety of cars at 70 into a concrete block - all would have proved fatal whether a big saloon or a Smart car.
Here ya go:
www.youtube.com/watch?v=Q91UIYquAW8
Edited by Lygonos on 09/05/2009 at 21:44
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>>Doubling the speed quadruples the energy.
But, the point I'm making is that the speed isn't actually being doubled. The speed of either car relative to the impact is still 35. The other car merely provides the same reaction as a huge block of concrete.
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If two cars are travelling at 35mph towards each other, the (combined) approach speed for both is 70mph.
Same if one car is doing 30mph and the other 40mph.
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NC has it right. It's like driving at 35mph not into a concrete block, but into another car which is a lot squashier than a concrete block. The cars' inertia, roughly equal, is cancelled out.
In practice much would depent on any skew, the way the cars bounced, what the drivers' heads hit and so on.
I can't say I would choose to do it in stunt-man mode but I would put the chances of survival, even non-injury, quite high for the drivers.
Edited by Lud on 09/05/2009 at 21:49
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>>not into a concrete block, but into another car which is a lot squashier than a concrete block
No, I think that's taking it too far Lud.
Instead of something difficult and messy like a car, consider 2 snooker balls (A and B) going at the same speed, heading directly towards each other. After the impact, both balls recoil at (almost) the same speed, and the impact would have looked exactly the same if instead of hitting another snooker ball, ball A had hit a perfectly rigid surface.
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Thank you Lygonos.
I was taught E=1/2M x c(squared)
Nowadays it seems to be E=M x C(squared)
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Thank you Lygonos. I was taught E=1/2M x c(squared) Nowadays it seems to be E=M x C(squared)
Crikey!
You want to keep those c squareds away, that's a LOT of energy.
E=m * c^2 is the amount of energy that could be released 100% of an object's mass was converted to energy.
E=1/2 m * c^2 is a new one to me, but I think you're probably thinking of the equation for Kinetic Energy, (given by another poster above):
KE = 1/2 m * v^2
They may not look much different but given that c usually stands as constant for the speed of light, you can see why it's not so applicable to vehicle energy, as fast as an Espace is, it can't quite manage 300,000 m/sec :)
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>>..as fast as an Espace is, it can't quite manage 300,000 m/sec :)>>
Unless The Stig's driving it?
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If light has been downgraded to 300km/sec it would explain the rubbish connection I've got today ;-)
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If light has been downgraded to 300km/sec it would explain the rubbish connection I've got today ;-)
hehe, if you're going to miss out a character, make it an important one :)
Incidentally, light can been slowed to 61kph, nearly the speed of an Espace, but it's rather hard to do.
www.hno.harvard.edu/gazette/1999/02.18/light.html
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Incidentally light can been slowed to 61kph nearly the speed of an Espace but it's rather hard to do. www.hno.harvard.edu/gazette/1999/02.18/light.html
Good to see that science writers understand the basic facts NOT......... quote from that article
" and temperatures almost a billion times colder that that in interstellar space, are needed"
p
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>>Good to see that science writers understand the basic facts NOT......... quote from that article
It sounds right to me.
What's wrong with it?
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If light has been downgraded to 300km/sec it would explain the rubbish connection I've got today ;-)>>
If you are using a modem router, try disconnecting the mains adapter lead for a second or so and then reconnecting the lead.
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Consider it another way. Imagine watching a high speed movie of 2 cars crashing - but the 2 cars are exact mirror images of each other and perfectly aligned with each other. The common impact surface will not move - therefore it would have made no difference had the impact being into a solid concrete block.
So, would it be right to think that, in the 2 x Espace test, the older car suffered more deformation than the newer one, so would have absorbed some of the impact energy of the newer car? Therefore there's a mismatch in the concrete block comparison - the newer car would have suffered less damage than if driven into a concrete block at 35MPH.
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>>Therefore there's a mismatch in the concrete block comparison
In reality, there always will be - the mirror image cars don't exist, and no real crash is perfectly aligned.
Yes, with disimilar cars, there will be a non-equal sharing of energy. The stiffer car effectively using the other as crumple zone.
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>> The stiffer car effectively using the other as crumple zone.
That's what we smug Volvo drivers like to say - You are my crumple zone!
( Although I thought another recent test showed that not to be true?)
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That's what we smug Volvo drivers like to say - You are my crumple zone! ( Although I thought another recent test showed that not to be true?)
You need some crumple otherwise you're dead - another TV crash with a Smart into a concrete block at 70MPH illustrated that. The Smart remained amazingly intact, but they reckoned the people inside would have died as they stopped so instantly.
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You need some crumple otherwise you're dead - another TV crash with a Smart into a concrete block at 70MPH illustrated that. The Smart remained amazingly intact but they reckoned the people inside would have died as they stopped so instantly.
>>
yup. The car can stop suddenly and suffer minimal damage, and nothing in the car will fatally come adrift and hit the driver.
However the driver is traveling at 70mph, and if he stops his internal organs do not. They carry on at 70mph, the heart mashing into ribs, the brain compressing against the front of the skull, al possibly fatally.
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