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Originally Posted by MAD
If your explanation is correct the tree impact will be less, if the other claim is correct, the impact with the tree will be no worse than that of the car so why hurt more people than necessary?
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Not quite. The consideration here has been full frontal impact, not a partial frontal impact. If you drive into a wall or another vehicle exactly the same as yours directly head on, then the forces are working on your vehicle across a much greater area than what would occur if you crashed into a tree or power pole.
For example, if some one was to throw a javelin at a tree, the javelin would penetrate into the tree because the forces involved in the impact work only on a very specific area of the tree. Now, if you get the same javelin, and instead of throwing it pointy end first, threw it side on instead, such that the entire length, rather than just the point, of the javelin impacted against the tree, then the javelin would not penetrate the surface of the tree.
I wouldn't like to take a guess as to which would be worse, hitting a power pole at 100km/h or hitting a another vehicle head on, that is also traveling at 100km/h in the opposite direction, at 100km/h. Given the seriousness of the injuries to anyone involved, I would have to agree with the paramedic (sorry, I can't remember who you are at the moment) who posted earlier, the two car collision will have more people involved, therefore it's worse.
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Flappist - I'll have one final attempt to explain the issue with the point of reference.
1. If you are standing still and I throw a ball at you at 20km/h, then when it impacts with you, you will feel the forces relative to the initial velocity of the ball and physical characteristics of the ball. To the observer watching this experiment, he sees me throw the ball at you at 20km/h, and the ball decelerate to 0km/h when it hits you.
2. Now, if instead of me throwing the ball at you, you run towards me at 20km/h. Just as you are about to get to me, I drop the ball in front of you, such that it impacts with you in the same spot as the ball I threw at you. As you are traveling at 20km/h and the ball is traveling at 0km/h at the time of impact, you will feel the same forces on the impact point as when I threw the ball at you at 20km/h and you were moving at 0km/h. This time however, the observer sees you running at the ball making impact, not the ball traveling to you making impact.
But, here's the thing with the point of reference. If you are the point of reference, so you only consider what you see through your eyes, and not what your body is doing, then even though you are running at the ball, to you, you see the ball coming towards you at 20km/h, even though the casual observer actually sees you running at the ball at 20km/h (you both have different points of reference - your own eyes).
3. So now if I combine both 1 and 2 and throw the ball at you at 20km/h and you run towards me at 20km/h, then the observer will see both objects (you and the ball) traveling at 20km/h towards each other.
When the ball hits you, you will feel the combined total affect of you traveling towards the ball at 20km/h and the ball traveling towards you at 20km/h.
From your point of view (through your eyes) you see the ball traveling towards you at 40km/h, and when it impacts with you, you will feel the forces relative to if the ball was traveling at 40km/h and you were standing still.
4. What I haven't told you till now is the ball I am throwing at you weighs exactly the same as you, and at the point of impact, both you and the ball a completely rigid.
Now this is what both the observer and you see.
The observer sees me throw a ball at you at 20km/h. The observer sees you run towards the ball at 20km/h. When you and the ball collide, the observer sees you decelerate from 20km/h to 0km/h, and the ball decelerate from 20km/h to 0km/h per hour. The observer therefore jumps to the conclusion that the forces you experienced would only be the same as if you'd run into a brick wall at 20km/h, and therefore you are only so injured.
From your perspective however, the events are very different. You see the ball weighing the same as you approaching at 40km/h. When the ball impacts with you, you see the ball decelerate from 40km/h to 0km/h per hour. You feel the forces acting on you relative to if the ball's actual velocity before the collision was 40km/h. Therefore the injuries you suffer are worse than if you had just run into a wall at 20km/h.
I hope this helps. If not, we will just have to agree to disagree.