Car physics

[auxr]

Sorry - now taking a bex & having a lie down, physics war has now begun

[Chopped]

The bat and ball theory is not correct because they are different masses, travelling at different speeds and have different levels of absorbency.

A more accurate test is to aim 2 baseballs at each other and let them hit each other - the balls will not fly out of park but rather drop down and roll back a little (like hitting a wall).

Both cars will hit what is in effect an invisible wall and then bounce back.

The same result will happen either way / This example proves it >

[Wally]

OK then lets look at the conservation of energy angle then:

Car A = E1
Car B = E2

E1 = E2

Combined energy is E1 + E2, in a head on the kinetic energy is shared equally between the two.

When Car A hits the immovable wall, energy will still be imparted into the wall as heat, sound waves, etc. The energy acting on the car must be less.

Chopped, did you never play conkers ? The balls not got thud and stop.

[flappist]

Originally Posted by Wally

OK then lets look at the conservation of energy angle then:

Car A = E1
Car B = E2

E1 = E2

Combined energy is E1 + E2, in a head on the kinetic energy is shared equally between the two.

When Car A hits the immovable wall, energy will still be imparted into the wall as heat, sound waves, etc. The energy acting on the car must be less.

Chopped, did you never play conkers ? The balls not got thud and stop.

No you don't get it wally.

The wall is immovable therefore no energy can pass to it.
Heat is movement.
Sound is movement.

If the wall can absorb some of the impact then it is not an immovable wall.

[MAD]

Originally Posted by Wally

OK then lets look at the conservation of energy angle then:

Car A = E1
Car B = E2

E1 = E2

Combined energy is E1 + E2, in a head on the kinetic energy is shared equally between the two.

When Car A hits the immovable wall, energy will still be imparted into the wall as heat, sound waves, etc. The energy acting on the car must be less.

Chopped, did you never play conkers ? The balls not got thud and stop.

Do any balls go thud and stop if you roll them at an immovable wall?


In an impact between Car1 and Car2, Car1 will impart all of its energy to Car2 and Car2 will impart all of its energy to Car1.

The immovable wall will reflect any impact and therefore impart Car1's energy back to Car1.

[RedHotGT]

Originally Posted by flappist

Exactly wrong loftie.

If one is stationary and immovable it must absorb the energy of the other object while that object collapses. The point of collision is fixed.
If both objects are identical then each absorbs the same amount of energy at the same rate and the point of collision is still fixed..

If you roll a perfect rubber ball at 10m/s into a wall it bounces off at 10m/s
If you roll the same rubber ball at 10m/s into another rubber ball at 10 m/s the BOTH bounce back at 10 m/s.

In immovable object MUST be exactly equivalent to an identical object travelling in the opposite direction OR ELSE IT WOULD MOVE.....

Ask your dad again, giving him all the details.......

Well I suppose we ARE going to be silly about this then.... Are we?

Name ONE entirely IMMOVABLE object... because as far as I know there is no material in this world that is IMMOVABLE....
because every single object in the world is going to have some sort of flexibility to it....

And if course if we're going to be silly about this... then lets calculate air resistance also, and take in to account how likely that an identical car with identical weight travelling at identical speeds on identical road surfaces are going to have a head on accident...

So instead of Over analyzing the question... Lets be simple and straight forward...

Like I said above... if YOU were driving in a vehicle and hit a stationary object (i'd better not say IMMOVABLE)... for instance - the side of a building... would that be as bad as having a head on accident (for example, driving down the wrong side of a freeway) at 100km/h...

Flappist - the rubber ball scenario is flawed in many ways which I won't go into (friction, air resistance, etc) otherwise if you had the ball bounce off two opposing walls, with your theory the ball would continue bouncing forever.... which it wouldn't....

And again using the 'rubber ball' theory, are you saying that the cars would simply bounce off each other and continue at 100km/h the opposite direction? Of course you aren't....

I'm sure we could go on about this all day long... but lets go to first post and answer the question....???

[SB076]

One of the significant things to take into consideration is the time of the accident (I studied this in year 11 physics - which was nearly 15 years ago) The other thing to take into consideration is change in direction. The human body can only take so much deceleration or change in direction.

For example you could have two cars crash head long both travelling in excess of 100k's an hour. But even though this isnt possible lets say the time of impact (the time taken from when one car first makes contact with the other car is 1 minute, due to let say special crumple zones - again I know this isnt possible) Both drivers (assuming they didnt make contact with anything) would survive. As the time if impact is long

However if you had two cars traelling in opposite directions both travelling at 20k's an hour and the time of of impact is 0.001 m/s then neither would surviive.

[MAD]

http://www.break.com/index/concreteplane.html

I'd say that's pretty immovable...haha

[4Vman]

Originally Posted by loftie

Well I suppose we ARE going to be silly about this then.... Are we?

Name ONE entirely IMMOVABLE object... because as far as I know there is no material in this world that is IMMOVABLE....
because every single object in the world is going to have some sort of flexibility to it....

And if course if we're going to be silly about this... then lets calculate air resistance also, and take in to account how likely that an identical car with identical weight travelling at identical speeds on identical road surfaces are going to have a head on accident...

So instead of Over analyzing the question... Lets be simple and straight forward...

Like I said above... if YOU were driving in a vehicle and hit a stationary object (i'd better not say IMMOVABLE)... for instance - the side of a building... would that be as bad as having a head on accident (for example, driving down the wrong side of a freeway) at 100km/h...

Flappist - the rubber ball scenario is flawed in many ways which I won't go into (friction, air resistance, etc) otherwise if you had the ball bounce off two opposing walls, with your theory the ball would continue bouncing forever.... which it wouldn't....

And again using the 'rubber ball' theory, are you saying that the cars would simply bounce off each other and continue at 100km/h the opposite direction? Of course you aren't....

I'm sure we could go on about this all day long... but lets go to first post and answer the question....???

The solution to your problem lies in post 1.. READ it properly and absorb the question posed before getting off on a tangent.....

[RedHotGT]

Originally Posted by 4Vman

The solution to your problem lies in post 1.. READ it properly and absorb the question posed before getting off on a tangent.....

Agreed...

So what is your take 4Vman??

The question asked is WHAT IS WORSE.... ??
Worse for who? or What?
Worse for the driver(s), the car? Worse for the tow truck that picks the carnage up??

[SB076]

Originally Posted by XCPWSF

I was wondering about this just before and I can't remember any of my yar 11 physics stuff, but would hitting a solid imovable object at 100km/h be worse than hitting another car head on also travelling at 100km/h?

To answer your question we need more info - as I said the human body only takes such much deceleration - your best chance is to extend the duration of the collision or minimise the change in direction this would increase your chance of survival.

My CAT (year 11 physics) was based on a person that jumped out of a 14 story building and lived - he landed on a roof of a car which completly collapsed but increase the time of the collision thus enabling him to survive - had he hit the pavement he wouldnt have been so lucky.

[flappist]

Originally Posted by loftie

Well I suppose we ARE going to be silly about this then.... Are we?

Name ONE entirely IMMOVABLE object... because as far as I know there is no material in this world that is IMMOVABLE....
because every single object in the world is going to have some sort of flexibility to it....

And if course if we're going to be silly about this... then lets calculate air resistance also, and take in to account how likely that an identical car with identical weight travelling at identical speeds on identical road surfaces are going to have a head on accident...

So instead of Over analyzing the question... Lets be simple and straight forward...

Like I said above... if YOU were driving in a vehicle and hit a stationary object (i'd better not say IMMOVABLE)... for instance - the side of a building... would that be as bad as having a head on accident (for example, driving down the wrong side of a freeway) at 100km/h...

Flappist - the rubber ball scenario is flawed in many ways which I won't go into (friction, air resistance, etc) otherwise if you had the ball bounce off two opposing walls, with your theory the ball would continue bouncing forever.... which it wouldn't....

And again using the 'rubber ball' theory, are you saying that the cars would simply bounce off each other and continue at 100km/h the opposite direction? Of course you aren't....

I'm sure we could go on about this all day long... but lets go to first post and answer the question....???

While you were/are at school did you learn to read?

READ what I wrote.
READ the first question.

Ask someone what is meant by a "perfect" rubber ball with regard to demonstrating principles. It means there is no friction or losses of any kind.

You have made a pork chop of yourself loftie, stop digging a deeper hole...

[Auslandau]

I have absolutley no knowledge (or want to) of physics as it was not good for your health and well being back in my school days .... but just logically .....

IF a fly hit your windscreen while doing 100km/h (the car, not the fly) he would be worse off than hitting a stationary object? I have witnessed both with my own eyes ..... trying to get out through a kitchen window compared to hitting my windscreen.

I look at is as common sense and not a formula that can be manipulated to make the fly bounce off the cars window and happily go about its day .... unless common sense has been replaced by an equation?



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[Franco Cozzo]

Well to clarify the question, what would be worse for the driver? What does he/she/it have a better chance of coming out alive from?

[Auslandau]

Originally Posted by loftie

Well I suppose we ARE going to be silly about this then.... Are we?

Name ONE entirely IMMOVABLE object... because as far as I know there is no material in this world that is IMMOVABLE....
because every single object in the world is going to have some sort of flexibility to it....

If I drove my car into Ayres Rock I am sure I'll flex before it does ...

This is a discussion and can see absolutley no reason for anyone to get in a twist about a theory that I am sure can be proved through physics but untill someone comes up with the 'Be all and end all' answer ...... there will be opposeing views so everyone will just have to live with that and not get knickers in knots.



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[4Vman]

Originally Posted by auslandau

I have absolutley no knowledge (or want to) of physics as it was not good for your health and well being back in my school days .... but just logically .....

IF a fly hit your windscreen while doing 100km/h (the car, not the fly) he would be worse off than hitting a stationary object? I have witnessed both with my own eyes ..... trying to get out through a kitchen window compared to hitting my windscreen.

I look at is as common sense and not a formula that can be manipulated to make the fly bounce off the cars window and happily go about its day .... unless common sense has been replaced by an equation?

When i was a kid i used to put flys in my air rifle and shoot them at walls (and people).. they made an awful mess and stung like crazy! Much like sticking your head out of a car window or riding a bike at 100kph and coping one in the face..
The fly couldn't "fly" fast enough itself to do that kind of damage though, it needed "supercharging" from compressed air to help!

But i digress...

[4Vman]

Originally Posted by loftie

Agreed...

So what is your take 4Vman??

The question asked is WHAT IS WORSE.... ??
Worse for who? or What?
Worse for the driver(s), the car? Worse for the tow truck that picks the carnage up??

READ the thread, i made my observations early on...

[Auslandau]

Originally Posted by 4Vman

When i was a kid i used to put flys in my air rifle and shoot them at walls (and people).. they made an awful mess and stung like crazy! Much like sticking your head out of a car window or riding a bike at 100kph and coping one in the face..
The fly couldn't "fly" fast enough itself to do that kind of damage though, it needed "supercharging" from compressed air to help!

But i digress...

Unless it jumps off a very tall building? Is that introducing another law of physics ....... ?

And yes I digress aswell and have given myself and 4Vman a warning for off topic chat .... back to the matter at hand



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[greenfoam]

I'll vote for a concrete bridge support being worse than a head on. I've seen picture of both kind of crashes over the years, the concrete allways seems to cause more damage. Just because in head on's cars will deflect, they will break in half and continue moving etc. As for a car with big mass vs small mass. The smaller car will allways change direction faster so is much less likely to be involved in the accident in the first place and is the safer car despite being damaged worse than a heavier car in a head on collision (assuming it doesn't deflect off the heavier car at a survivable amount of G's).

Landcruiser vs Barina could easily see them both swerve with the Cruiser rolling into a tree, while the Barina was ok

[auxr]

Originally Posted by 4Vman

When i was a kid i used to put flys in my air rifle and shoot them at walls (and people).. they made an awful mess and stung like crazy! Much like sticking your head out of a car window or riding a bike at 100kph and coping one in the face..
The fly couldn't "fly" fast enough itself to do that kind of damage though, it needed "supercharging" from compressed air to help!

But i digress...

bwa ha ha - off topic I know, couldn't help myself.

[Auslandau]

Originally Posted by greenfoam

As for a car with big mass vs small mass. The smaller car will allways change direction faster so is much less likely to be involved in the accident in the first place and is the safer car despite being damaged worse than a heavier car in a head on collision (assuming it doesn't deflect off the heavier car at a survivable amount of G's).

Landcruiser vs Barina could easily see them both swerve with the Cruiser rolling into a tree, while the Barina was ok

I think that has already been decided as a given. The discussion is on two objects the same size ..... comparing when an apple hits an apple .... not a watermelon hitting a grape. (If 87 year old Grandma was driving the Barina .... )?



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[geckoGT]

Originally Posted by Brazen

Hitting an immovable object is the equivalent of hitting a car with the same mass at the same speed from the opposite direction, how many cars on the road are the same mass as a 1000kg Fiesta?

The point I was making is that a Fiesta gets the 5 star rating in a test which is the equivalent of hitting another Fiesta head on (ie same mass), the Fiesta isnt tested against hitting an object of greater mass (ie against a Falcon or a Landcruiser) - This has been demonstrated is numerous tests including a 4 star Audi SUV (greater mass) hitting a 5 star Smart car (smaller mass), the results were minor injuries to the Audi driver with life-threatening injuries to the Smart driver. The Smart gets its 5 star rating hitting the equivalent of another Smart at the same speed, not against hitting the average vehicle on the road.

The Ancap tests are good for comparing cars which are hitting trees or solid walls, they are not good seeing what the results would be hitting other cars where differences in mass come into play.

You have missed my point.

ANCAP uses 4 internationally recognized crash tests; offset frontal, side impact, pedestrian and pole impact test.

Crash tests are undertaken by independent specialist crash test laboratories.In all tests crash test dummies are used to facilitate the scientific measurement of the various forces in the crash test. The data gathered is then assessed, using internationally recognized protocols, and scores are determined for various parts of the crash test. Additionally, ANCAP awards bonus points for other safety features such as seat belt reminders.

The overall score is then translated into a star rating, between 1 to 5 stars. The higher scores are awarded more stars
The offset frontal crash test simulates colliding with another vehicle.

Frontal impact takes place at 64kph and the car strikes deformable barrier. The vehicle has 2 adult dummies in the front seats. The rear seats have an 18 month old and 3 year old child dummies in appropriate child restraints

So both vehicles have hit the same barrier, at the same speed and along the same vector. The testing measures the forces applied to the dummies at key know injury points. This data is scored and subsequently a rating is allocated, the higher the rating, the lower the chance of injury. That is the only fair way to compared different makes and types of vehicles.

By your logic all large cars would automatically score higher than small cars because your theory is a small car will sustain more damage and cause more injury if hit by a large car. That is an incorrect assumption as many small cars have demonstrated similar injury causing force loads on occupants as many larger cars when hitting the same barrier. You can not say that this testing is flawed because if the small car hits a 4wd it will cause more injury, if the large car hits a B double it will cause injury too. The point is, within the scope of the test (which closely mimics a offset frontal crash with another car at with an impact speed of 64 km/h) both cars perform the same.
Your theory is flawed when you look at the results. Out of the 4wd vehicle (I picked these because of the common belief they are safe), very few achieve a 5 star rating, it seems the larger they are the worse they do with landcruiser and patrol only get 4 and 3. It is not until you get to smaller models such as santa fe and X5 that you get 5's. Looking at current models, this class has an average of 4.3 stars.
Large car such as falcon, aurion and commodore get 4 or 5 depending on year. Looking at current models, this class has an average of 4.75 stars. Small have an interesting fact that a lot of the cheaper cars score poorly but the europeans and more expensive options such as fiesta and focus score well. Looking at current models, this class has an average of 4.4 stars.

For ancap to provide a rating that satisfies your doubts, it would involve too many crash tests to be economically viable for manufacturers and end in results that are too complex and time consuming as a car is smashed in many different vectors, at different speeds, against smaller, same size and larger cars (or barriers to replicate this). Then this would all end up as information that is lost on the car buying public as they are not interested in trying to decipher it and will probably by the one with more creature comforts, goes faster, looks prettier etc rather than the one that is genuinely safer.

Really, what is the point of all this discussion? The end result is in both instances the forces involved are far outside the scope of any safety system in any car on the road and both impacts are highly likely to result in fatalities and/or serious injury no matter what you drive. Trust me, I scrape the results out of the wrecks for a living. I am not just talking seeing pictures, I am talking in the car with the casualties and treating their wounds. The results would be virtually no different, once you have exceeded the limit of the human body to withstand human force, you get injury. I can tell you in both instances the injuries are most likely to be fatal, at least all the ones I have been to involving these forces have been.

[RedHotGT]

Yeah ok - I suppose the bottom line is this:

Either way - you're screwed....

[geckoGT]

Lets look at the question a different way.

In scenario 1, it involves 1 car into a solid object at 100, up to 5 dead or seriously injured and the result of a fault in the driver of that car.

In scenario 2 you have 2 cars, up to 10 dead and seriously injured, one vehicle is likely to be innocent and not the cause of the accident.

The paramedic in me says the second scenario is much worse as there are more dead and injured, as well as innocent people being involved.

Who gives a toss about the amount of force involved, it is the result that matters.

[RedHotGT]

Originally Posted by flappist

While you were/are at school did you learn to read?

READ what I wrote.
READ the first question.

Ask someone what is meant by a "perfect" rubber ball with regard to demonstrating principles. It means there is no friction or losses of any kind.

You have made a pork chop of yourself loftie, stop digging a deeper hole...

I understand 'perfect' theories for explaining and demonstrating principles...
Its the very reason arguments occur... because 'perfect' situations never actually happen... There is always a variable that will make a particular example different from the 'perfect world scenario'...

I did read what you wrote Flappist... and I did read the first question...

No hole dug.... but thank you for reminding me what I need to do in my yard... My turtle enclosure is way behind schedule... *(off topic SLAP)*

[talk2tiny]

I realise that there's no reason to trust my credibility any more than anyone else who's posted here but if you're interested, I have degrees in mathematics and theoretical physics and have almost completed a PhD in theoretical quantum physics. I can assure you that from a purely mathematical standpoint, two solid objects travelling at 100km/h towards each other results in the exact same forces as a single object travelling at 200km/h hitting a stationary object.

It's all to do with relative velocities but I won't go into the details. Those who don't believe me yet won't be swayed by a proof either. Obviously I can't speak for the effects of crumple zones and glancing collisions etc but to answer the physics part of the question, definitely aim for the wall rather than the car.

[XR6_661]

The AFF scientists strike again!

[geckoGT]

Originally Posted by talk2tiny

I realise that there's no reason to trust my credibility any more than anyone else who's posted here but if you're interested, I have degrees in mathematics and theoretical physics and have almost completed a PhD in theoretical quantum physics. I can assure you that from a purely mathematical standpoint, two solid objects travelling at 100km/h towards each other results in the exact same forces as a single object travelling at 200km/h hitting a stationary object.

It's all to do with relative velocities but I won't go into the details. Those who don't believe me yet won't be swayed by a proof either. Obviously I can't speak for the effects of crumple zones and glancing collisions etc but to answer the physics part of the question, definitely aim for the wall rather than the car.

Thankyou, someone who actually knows what they are talking about in regards to the physics.

One problem, you talk of a car into a stationary object at 200 km/h, the question of the OP asked about a car traveling at 100 km/h hitting a stationary object compared to two cars in a head on both traveling at 100 km/h.

What is your opinion of the forces involved, are they equal or is one more than the other in this comparison?

Need to be real clear otherwise your answer will get picked to death and discussed for another 2 days.

[jimby]

newtons 3rd law

[MAD]

Originally Posted by talk2tiny

I realise that there's no reason to trust my credibility any more than anyone else who's posted here but if you're interested, I have degrees in mathematics and theoretical physics and have almost completed a PhD in theoretical quantum physics. I can assure you that from a purely mathematical standpoint, two solid objects travelling at 100km/h towards each other results in the exact same forces as a single object travelling at 200km/h hitting a stationary object.

It's all to do with relative velocities but I won't go into the details. Those who don't believe me yet won't be swayed by a proof either. Obviously I can't speak for the effects of crumple zones and glancing collisions etc but to answer the physics part of the question, definitely aim for the wall rather than the car.

Looking at this with static analysis the outcome is different, as has been mentioned.
Eg. Having a force of 100kg applied at each end of a steel rod, for example, does not equate to 200kg of force in the middle.

Could you put up a bit of detail that shows how your analysis is different?