- #1

ninuss

- 2

- 0

https://www.physicsforums.com/threads/relative-speed-of-two-cars.642873/

https://www.physicsforums.com/threads/two-cars-colliding.740948/

And gathered what I already thought was correct, that the relative velocities of two cars of equal mass crashing into each other are the same in examples 1) and 2),

where in example 1), car X is moving a 100km/h in a straight line towards car Y, and car Y is moving at 100km/h in a straight line towards car X;

and in example 2), car X is moving at 200km/h in a straight line towards car Y, and car Y is moving at 0km/h towards car X (car Y is standing still)

Now, my question is, would the crashes in these two examples produce the same kind of damage to the cars? I was told that in example 2, the kinetic energy released is twice as much as in example 1, because kinetic energy is calculated by squaring velocity, and so simply adding the velocity of each car and then squaring it, is not the same as squaring each and then adding it.

But my thinking is that if the relative velocity is the same, the crash should be the same..

In example 1), both cars would roughly come to a full stop (or they may bounce a little), and in example 2), after the crash, both cars would continue moving in the same direction as car X, but at a slower speed. That's the only difference I can come up with. But it still makes no sense to me that the damage would be doubled when the relative velocity is the same.