81
Physics, Astronomy & Cosmology / Re: Why does double the velocity double the momentum and quadruple the KE?
« on: 29/09/2021 21:12:26 »
Heh, missed the second page. It seems that you do? Assume that the the momentum of something isn't there if it is of a speed, equal to what it collides with?
Is that correct?
=
Both cars use earth as their relative frame of no motion. and both cars are moving at a same speed relative earth. You put up a rock in front of any of those cars and the kinetic energy will exist, being the same for both occasions, assuming the cars to be identical clones :) as well as the speed etc.
So that kinetic energy must exist as a momentum for both cars and will transform into kinetic energy at a collision. So it should be the same as if you collide with that rock at a hundred, or crash head-on, doing fifty, into that other car, it too doing fifty although in the opposite direction.
But it is weird, momentum and kinetic energy. You could define something else than earth as your 'stationary point', some patch of space that earth swish by in its 'relative motion' through the universe. At least in relativistic terms. Then vectors and speeds relative that motion will come in and play a role for how that collision will be interpreted etc. But it won't change the kinetic energy involved in the 'system' colliding. So suddenly it's not relative anymore, or is it?
Is that correct?
=
Both cars use earth as their relative frame of no motion. and both cars are moving at a same speed relative earth. You put up a rock in front of any of those cars and the kinetic energy will exist, being the same for both occasions, assuming the cars to be identical clones :) as well as the speed etc.
So that kinetic energy must exist as a momentum for both cars and will transform into kinetic energy at a collision. So it should be the same as if you collide with that rock at a hundred, or crash head-on, doing fifty, into that other car, it too doing fifty although in the opposite direction.
But it is weird, momentum and kinetic energy. You could define something else than earth as your 'stationary point', some patch of space that earth swish by in its 'relative motion' through the universe. At least in relativistic terms. Then vectors and speeds relative that motion will come in and play a role for how that collision will be interpreted etc. But it won't change the kinetic energy involved in the 'system' colliding. So suddenly it's not relative anymore, or is it?
The following users thanked this post: Curious Cat