So if my energy equation is correct and my first equation is also correct (hard to calculate that one wrong), what am I supposed to do? Is there an equation that I have not considered? I already tried swapping things from on formula to another but they don't equal the same thing for V1 + V2 so...
Since the mass of both vehicles is the same, it's possible to calculate Ki which happens to be 512,5J and from there, multiply it by 0,25 since 75% of the energy is gone and I end up with 128,125J.
Now my problem is that for the velocity, I have: 25,0 + -20,0 = V1 + V2 which is 5,00 = V1 + V2...