Police get riders at over 200 km/h

[Jantar]

Yes the momentum is conserved.

However you have redefined your argument (which is a common rhetorical trick).

In your original post you made absolutely no reference to what kind of vehicle the observer was traveling in, and then in your reply you have suddenly specified that the observer is traveling in a car......

I don't see any re-defining of the argument. It doesn't really matter what vehicles are involved, as Mikkel points out its the conservation of momentum that will dtermine the final outcome, not the dissipation of energy.

If it was solely the dissipation of kinetic energy that decided whether or not a person was killed or injured in a crash then it would be possible to calculate the exact velocity at which this would occur, and it wouldn't matter whether someone hit a tree and stops instantly, or slides along the ground on a slippery surface for hundreds of meters while slowing down gradually. They would both die.

Using the kinetic energy argument is just another method that the PTB use to convince the uneducated that all speed is dangerous.

[Mikkel]

My point was only that introducing a discussion of momentum only makes sense if you know the specific masses and velocities of both parties that are involved in the collision.

If you don't know the masses and velocities of the colliding vehicles then you cannot draw a general conclusion.

Oh, I am not going to dispute that. But since we are engaging in a thought experiment here we do have the luxury of setting the variables however we like. However, it seemed to me that your point was that I was "Completely wrong" because I didn't calculate the kinetic energy of the vehicles...

As I have often asserted before in other discussions - most real-life situations are too complicated to actually calculate exactly. The art is in removing the small things that doesn't have a significant impact from the equation (e.g. localised heat distribution in the tyres and its impact upon traction, angular momentum carried by the flywheel at the time of impact...) so you end up with something which can actually be calculated. If you follow that through to its natural conclusion you'll end up with the conservation of momentum. It is the very fundament for analysing impacts - you then build layer upon layer of complexity on top of that (conservation of angular momentum first then maybe conservation of energy).

[Forest]

I don't see any re-defining of the argument. It doesn't really matter what vehicles are involved, as Mikkel points out its the conservation of momentum that will dtermine the final outcome, not the dissipation of energy.

It does matter which vehicles are involved.

There's a world of difference between hitting a bicycle, and hitting a bus.

If it was solely the dissipation of kinetic energy that decided whether or not a person was killed or injured in a crash then it would be possible to calculate the exact velocity at which this would occur, and it wouldn't matter whether someone hit a tree and stops instantly, or slides along the ground on a slippery surface for hundreds of meters while slowing down gradually. They would both die.

Using the kinetic energy argument is just another method that the PTB use to convince the uneducated that all speed is dangerous.

The kinetic energy of a moving vehicle is transferred into any object that it collides with. This includes oncoming vehicles.

More kinetic energy = bigger collision.

This is simple and unarguable.

[Mikkel]

The kinetic energy of a moving vehicle is transferred into any object that it collides with. This includes oncoming vehicles.

More kinetic energy = bigger collision.

This is simple and unarguable.

That is both simple and wrong.

[Pixie]

If you are in your car you WILL prefer to be hit by a motorcycle at 211 km/h compared to a car at 95 km/h. (The point of impact and other circumstances being the same). If you are travelling in a car (1000 kg) at 100 km/h and have a frontal collision with a bike (200 kg) travelling at 200 km/h you will continue travelling forward at 50 km/h. If you have a collision with another car (1000 kg) travelling at 100 km/h you will come to a complete stop - what do YOU think will hurt the most?

[

Ha Ha what a croc.
You may as well say you would prefer to be hit with a bullet carrying 1000 ft /lbs of kinetic energy than a loose bag of feathers with the same energy

[Mikkel]

Ha Ha what a croc.
You may as well say you would prefer to be hit with a bullet carrying 1000 ft /lbs of kinetic energy than a loose bag of feathers with the same energy

If you don't understand something, you probably shouldn't comment on it. For starters "ft /lbs" is not a unit for energy - "ft * lbs" is, there is a slight difference.

Sorry, you fail.

[Forest]

That is both simple and wrong.

It is correct to a first approximation.

A more precise answer depends on the coefficient of restitution (but that obviously depends on the type of collision we are studying).

More kinetic energy = bigger collision

[Mikkel]

The kinetic energy of a moving vehicle is transferred into any object that it collides with. This includes oncoming vehicles.

More kinetic energy = bigger collision.

This is simple and unarguable.

It is correct to a first approximation.

A more precise answer depends on the coefficient of restitution (but that obviously depends on the type of collision we are studying).

More kinetic energy = bigger collision

What I have here highlighted from your previous post are two incorrect statements. 1) The kinetic energy is not transferred into the other body - that is an incorrect description. 2) Simplistic yes, however even considering a statement unarguable is an error of logic. For starters you have to explain what you mean by bigger - are we talking larger volume? More deadly? What? It's like saying a GSX-R1000 is bigger than a VFR800 - not incorrect as such, but not exactly 100% true either.

There's no insight in the "more kinetic energy = bigger collision" statement - it's no different from saying "bigger truck = bigger collision" or "the faster you go = the bigger the mess". It's not untrue - but it doesn't provide an ounce of understanding either.
All I am trying to get across is that the scale of an impact is proportional to both the masses and the velocities - not the square of the velocity as with kinetic energy.

[Forest]

What I have here highlighted from your previous post are two incorrect statements. 1) The kinetic energy is not transferred into the other body - that is an incorrect description.

The energy is most certainly transferred into the other body. The degree of energy transfer depends on the coefficient of restitution (which determines the degree of inelasticity).

2) Simplistic yes, however even considering a statement unarguable is an error of logic. For starters you have to explain what you mean by bigger - are we talking larger volume? More deadly? What? It's like saying a GSX-R1000 is bigger than a VFR800 - not incorrect as such, but not exactly 100% true either.

Bigger = more energetic

That should have been obvious from the context.

There's no insight in the "more kinetic energy = bigger collision" statement - it's no different from saying "bigger truck = bigger collision" or "the faster you go = the bigger the mess". It's not untrue - but it doesn't provide an ounce of understanding either.
All I am trying to get across is that the scale of an impact is proportional to both the masses and the velocities - not the square of the velocity as with kinetic energy.

The severity of the impact is proportional to the energy of the colliding objects, and the energy is proportional to the square of the velocities.

[Jantar]

The energy is most certainly transferred into the other body. ....

Wow, This is great news. If you are correct I can ride my suzu 1000 at high speed into a concrete wall and not only will the bike remain undamaged, but I'll suffer no injuries at all because all that kinetic energy will transferred into the wall.

Somehow I don't think I'll risk it. I'll continue to believe in conservation of momentum, and energy being disapated into both bodies according to function of force x distance. As the wall wont move, then all the energy would be disapated with my own body and the bike. That seems both painful and expensive and lines up with what we know to happen in practice.

[thepom]

god your all so boring....get a life.....

[Mikkel]

The energy is most certainly transferred into the other body. The degree of energy transfer depends on the coefficient of restitution (which determines the degree of inelasticity).

I can assure you that no kinetic energy is being imparted into the other body during a collision. What you are saying is equivalent to the other body speeding up during the impact - that would emply a negative mass if that should make sense physically.

Bigger = more energetic

That should have been obvious from the context.

So what you are saying is: "more kinetic energy = more energetic collision". How profound.

The severity of the impact is proportional to the energy of the colliding objects, and the energy is proportional to the square of the velocities.

Again, you are mistaken - or at the very least guilty of over-simplificating the matter.

[short-circuit]

over-simplificating.

There's no such word.

Fuck this thread is boring

[Thani-B]

There's no such word.

Fuck this thread is boring

I agree. I was enjoying reading this thread but its over the top now

[Butch]

I agree. I was enjoying reading this thread but its over the top now

Too many people thinking the more posts they make the better it makes them...

Get of the keyboard and get out and ride your bikes!

The original post of this thread was about them guys getn busted for a little speed, personally I dunno why they stoped, must have been running low on gas or something leggit...