Consider two solid objects: A and B.
A <----- B 10m/s
A -----> B 10m/s
They are identical except for the reference frame.
Common relativity tells us they are equivalent and will evolve in the same way, right?
Now add masses: A weights 1kg and B weighs 10kg.
In system 1, B will hit A with 500J of kinetic energy. In system 2, A will hit B with 50J of kinetic energy.
So... the energy involved in the impact (and effects such as how far debris is flung) depends on what reference frame I'm in? This doesn't seem right.
How do we resolve this?