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Speed Kills Or Inability Of Use Of Speed?

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1. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by oo00oo)
I agree that speed doesn't cause harm directly, it's acceleration.
That's what JC's quote said, and you said it wasn't true (please don't tell me you're nit-picking because it said stopping and not sudden acceleration).

But it doesn't matter whether it's acceleration or deceleration - both have the same result.

Sudden acceleration in any direction (i.e. positive acceleration or deceleration) has the exact same effect on the body.

If you go from 70 to 0 in a few short seconds or less, it's just as damaging and dangerous as going from 0 to 70 in the same time frame.

Now, if you're IN a car, then yes, chances are you won't be accelerating from 0 to 70 from engine acceleration in the same time frame that you can go from 70 to 0 in a crash. BUT, if you are a pedestrian being struck by a car, then you WILL be being accelerated from near 0 to a very high speed in an instant. So in that case, the acceleration will kill the pedestrian.

Similarly if you're in a car at a low speed and get hit by a car at a higher speed, the sudden acceleration will almost certainly kill you.

Speed doesn't kill, acceleration (or deceleration) does... but the speed of the car determines the acceleration of the pedestrian or the acceleration of the other car. So in an indirect way, the speed of a vehicle is responsible for the amount of acceleration which occurs during the crash and thus, is responsible for the level of injury and any deaths involved.
Not true actually - the human body can much better withstand high G forces facing backwards, for example. Read up on John Stapp - he subjected himself to G forces in excess of those experienced by a car at 120mph hitting a brick wall. Racing drivers have experienced 100g and survived. There's a lot more to it than just magnitude of acceleration (and it's force, not acceleration itself, that is damaging).
Oh, and a pedestrian will only accelerate to a very high speed if the car was travelling at a very high speed - the car is only accelerating them whilst it is in contact with them, and by the time the pedestrian is going the same speed as the car they are no longer being accelerated.
Last edited by CurlyBen; 21-05-2012 at 19:12.
2. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by CurlyBen)
That's what JC's quote said, and you said it wasn't true (please don't tell me you're nit-picking because it said stopping and not sudden acceleration).
It wasn't true though... the part about 'speed' itself not being the culprit directly is true, but the part about 'sudden stopping' being the culprit was at least only part of the truth... sudden stopping or sudden starting is what hurts - acceleration or deceleration.

The quip is misleading because it intends to tell us that going fast in your car isn't the problem, it's slowing down in your car too quickly that's the problem. From the point of view of the driver having a crash into a wall, then yes, that's the case... flying at 100mph, you're safe in your car. Stopping very suddenly from 100mph, and you're flying through the windscreen.

But from the point of view of one car being smashed into by another with a much higher speed, or from the point of view of a pedestrian being hit by a car, then the extent of the accident is always going to be directly related to the speed of the vehicle.

The sudden acceleration of a pedestrian is always dictated by the original speed of the car, so in an indirect way, speed is the culprit.

Not true actually - the human body can much better withstand high G forces facing backwards, for example. Read up on John Stapp - he subjected himself to G forces in excess of those experienced by a car at 120mph hitting a brick wall. Racing drivers have experienced 100g and survived. There's a lot more to it than just magnitude of acceleration (and it's force, not acceleration itself, that is damaging).
Whether you're hit from the front or the back doesn't make a massive difference where car accidents are concerned.

Force and acceleration are directly proportional, so to say that one is the cause rather than the other is really a moot point... Force is mass times acceleration, by Newton's 2nd law, and the mass of the pedestrian is, for the purposes of a car accident, not variable. So it's the acceleration and the acceleration alone which dictates the extent of their injury and the likelihood or their demise. And the acceleration is, of course, dictated by the velocity of the car that impacts them.

[/quote]Oh, and a pedestrian will only accelerate to a very high speed if the car was travelling at a very high speed - the car is only accelerating them whilst it is in contact with them, and by the time the pedestrian is going the same speed as the car they are no longer being accelerated.[/QUOTE]

The pedestrian's velocity changes from almost 0 to a very high speed in a very short period - hence, they experience a very high acceleration, which is what is responsible for their injury and/or death.

The period of time that they're in contact with the car is always very small, but the smaller the velocity of the car, the smaller the acceleration of the pedestrian, and the less their chances of injury and/or death are.

Don't make me bring out the equations.
3. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by oo00oo)
It wasn't true though... the part about 'speed' itself not being the culprit directly is true, but the part about 'sudden stopping' being the culprit was at least only part of the truth... sudden stopping or sudden starting is what hurts - acceleration or deceleration.

The quip is misleading because it intends to tell us that going fast in your car isn't the problem, it's slowing down in your car too quickly that's the problem. From the point of view of the driver having a crash into a wall, then yes, that's the case... flying at 100mph, you're safe in your car. Stopping very suddenly from 100mph, and you're flying through the windscreen.

But from the point of view of one car being smashed into by another with a much higher speed, or from the point of view of a pedestrian being hit by a car, then the extent of the accident is always going to be directly related to the speed of the vehicle.

The sudden acceleration of a pedestrian is always dictated by the original speed of the car, so in an indirect way, speed is the culprit.

Whether you're hit from the front or the back doesn't make a massive difference where car accidents are concerned.

Force and acceleration are directly proportional, so to say that one is the cause rather than the other is really a moot point... Force is mass times acceleration, by Newton's 2nd law, and the mass of the pedestrian is, for the purposes of a car accident, not variable. So it's the acceleration and the acceleration alone which dictates the extent of their injury and the likelihood or their demise. And the acceleration is, of course, dictated by the velocity of the car that impacts them.

Oh, and a pedestrian will only accelerate to a very high speed if the car was travelling at a very high speed - the car is only accelerating them whilst it is in contact with them, and by the time the pedestrian is going the same speed as the car they are no longer being accelerated.

The pedestrian's velocity changes from almost 0 to a very high speed in a very short period - hence, they experience a very high acceleration, which is what is responsible for their injury and/or death.

The period of time that they're in contact with the car is always very small, but the smaller the velocity of the car, the smaller the acceleration of the pedestrian, and the less their chances of injury and/or death are.

Don't make me bring out the equations.
Crack on - bring out the equations! Let's have some numbers - say a car doing 15mph hits a pedestrian. How can the pedestrian be accelerated beyond 15mph? Think about it this way - as soon as the pedestrian is doing 15.1mph it is moving away from the car, and is no longer in contact with it. If the car is no longer in contact, it can no longer exert a force. If a force is no longer being exerted on the pedestrian, it is no longer accelerating. Hence, for a pedestrian to reach 'a very high speed' the car must have been travelling at 'a very high speed'
As for the phrase - I'm not arguing semantics over a catchy phrase that is basically accurate. I've got better things to do.
If you want to argue about what causes injury in an accident go and do some research first - it's a lot more complicated than you're making it out to be. For example, if you don't see the ar coming you don't tense and injuries are lessened. Also the rapidity of onset of acceleration is important - go and read up about John Stapp. A little knowledge won't hurt.
4. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by CurlyBen)
Crack on - bring out the equations! Let's have some numbers - say a car doing 15mph hits a pedestrian. How can the pedestrian be accelerated beyond 15mph? Think about it this way - as soon as the pedestrian is doing 15.1mph it is moving away from the car, and is no longer in contact with it. If the car is no longer in contact, it can no longer exert a force. If a force is no longer being exerted on the pedestrian, it is no longer accelerating. Hence, for a pedestrian to reach 'a very high speed' the car must have been travelling at 'a very high speed'
I never said anything to the contrary of this... are you arguing with yourself? You don't have to be accelerated to beyond the speed of the car for it to count as "very high speed"... if the car is going fast enough, it will hurt you, and it may kill you. The speed of the car is the defining factor in the injuries that you sustain, as it is the speed of the car which determines how much you will be accelerated - which determines how much momentum will be transferred to your body.

End of story.

As for the phrase - I'm not arguing semantics over a catchy phrase that is basically accurate. I've got better things to do.
If you want to argue about what causes injury in an accident go and do some research first - it's a lot more complicated than you're making it out to be. For example, if you don't see the ar coming you don't tense and injuries are lessened. Also the rapidity of onset of acceleration is important - go and read up about John Stapp. A little knowledge won't hurt.
Rapidity of the onset of acceleration? What the hell is THAT supposed to be? The differential of acceleration, otherwise known as jerk, which is such a pointless derivative that in all my years of doing research in space physics, where objects undergo massive accelerations, I'd never had to deal with it or seen anybody deal with it?!

Please, don't argue Newtonian physics with a rocket scientist - you're wasting your time and making yourself look like an idiot.
5. Re: Speed Kills Or Inability Of Use Of Speed?
I think we should put the OP in a car heading towards a brick wall at 50mph and see how his knowledge saves him.
6. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by oo00oo)
I never said anything to the contrary of this... are you arguing with yourself? You don't have to be accelerated to beyond the speed of the car for it to count as "very high speed"... if the car is going fast enough, it will hurt you, and it may kill you. The speed of the car is the defining factor in the injuries that you sustain, as it is the speed of the car which determines how much you will be accelerated - which determines how much momentum will be transferred to your body.

End of story.
Funnily enough, I took a step back after my last post and realised this is daft. Your only contribution has been to point out the phrase JC posted is not limited to deceleration, which tbh most people probably already knew and is pretty pedantic. It's pretty damn obvious a high speed crash will probably be worse than a low speed crash, which seems to be your next argument.
However, acceleration is not the only factor in crash survivability. At the end of WWII the USAAF considered 18G lethal, so that's what cockpits were designed to survive. Since then John Stapp has strapped himself to a rocket sled and survived 46G (I don't mean to bang on about him, but he's pretty relevant) and NASCAR drivers have walked away from crashes which have seen them endure over 100G. On the other hand, many, many people have died from much less severe acceleration.
Another way of looking at it - a car crashes at 30mph into a low brick wall. The rear passenger is wearing a seatbelt and is subjected to a strong deceleration. The front passenger isn't wearing a seatbelt and goes through the windscreen, over the bonnet and wall before rolling to a stop, suffering a much less severe deceleration. Which passenger would you rather be?

Rapidity of the onset of acceleration? What the hell is THAT supposed to be? The differential of acceleration, otherwise known as jerk, which is such a pointless derivative that in all my years of doing research in space physics, where objects undergo massive accelerations, I'd never had to deal with it or seen anybody deal with it?!
If you know what it is, why are you asking? It's one of the 5 factors relating to acceleration mentioned in this article with regards to crash survivability. I quote "For a given magnitude and duration of acceleration, thegreater the rate of onset, the less tolerable the acceleration ". Maybe it's because space physics, or at least your bit, doesn't have much to do with squishy humans? After all, a well designed structure will stay intact whilst exposed to any forces within it's design parameters. One of the issues with human acceleration/deceleration is different bits accelerating at different rates. It gets messy when your internal organs are trying to move at a different speed to your torso.

Please, don't argue Newtonian physics with a rocket scientist - you're wasting your time and making yourself look like an idiot.
Oh that old chestnut. My first year mechanics module was shared with the astronautics guys and was delivered by a 'rocket scientist'. One of my third year modules was on bioengineering and we touched briefly on how the body reacts in collisions. Still, fortunately I'm not a cock, so I don't try and use my degree as some kind of trump card.
7. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by M4LLY)
I think we should put the OP in a car heading towards a brick wall at 50mph and see how his knowledge saves him.
A very intelligent reply there, we should pay you for advise like this.

But if you must know how I would apply my knowledge in your hypothetical situation, I will tell you.

So I am in a car moving in a direction heading towards a brick wall at 50 mph. I would then change my direction using the steering wheel in a manner such that I do not hit the brick wall. qed.
8. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by oo00oo)
I never said anything to the contrary of this... are you arguing with yourself?
(Original post by CurlyBen)
Funnily enough, I took a step back after my last post and realised this is daft.
Is it just me that's finding it difficult to establish what the hell you two are arguing about? At one point you were pretty much agreeing with each other without even realising

9. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by JO53PHS)
Is it just me that's finding it difficult to establish what the hell you two are arguing about? At one point you were pretty much agreeing with each other without even realising

It's not just you! It's been a good laugh reading through their arguments .
10. Re: Speed Kills Or Inability Of Use Of Speed?
I'll admit I slightly misinterpreted her first post - I didn't think anyone would be so pedantic, and that set me off.
That, and I hate simply being told I'm wrong, as Dan probably remembers from another recent thread
11. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by CurlyBen)
I'll admit I slightly misinterpreted her first post - I didn't think anyone would be so pedantic, and that set me off.
That, and I hate simply being told I'm wrong, as Dan probably remembers from another recent thread
12. Re: Speed Kills Or Inability Of Use Of Speed?
I am skilled at high speed, I come to roundabouts and lift off the throttle then take the racing line through it, same when I come to bends tight in, wide out and stick my fingers up at any oncoming cars, I also outbrake cars into corners
13. Re: Speed Kills Or Inability Of Use Of Speed?
After watching today's show on itv, it is just stupid.

I drive regularly, i've seen 1000's of drivers over 30 who are equally if not more dangerous than the ones that are 17 and 18.

It is a scientific fact that reaction times depreciate as one ages, so why are very elderly drivers not being retested to ensure they are road legal?

I would be in favour of changing the driving test to test actual road conditions. We get taught how to bay park, I dont think ive ever seen anyone in my life bay park like they make you do for the test, it is pointless. Why not focus on a way to teach drivers how to correct over steer and under steer, you know that could save many lives.

I have been enjoying the icy conditions recently, it is satisfying to know that I am in the top 1% of drivers, my techniques allow me to take better lines, progressively steer to ensure I have maximum grip. I can effectively demonstrate taking a corner safer at 40mph than someone of less ability at 20 mph.
14. Re: Speed Kills Or Inability Of Use Of Speed?
(Original post by konvictz0007)
x
Okay, let's just assume for a second that actually are the second coming of Michael Schumacher; you've completely missed the point here, and here's why:

-You are in the top 1% of drivers.
-Pretty much everybody else is not.

Ergo, speed limits are required.

Kbai

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Last updated: December 14, 2012
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