A low-energy particle collides elastically with a stationary particle of the same mass. The angle between the subsequent paths of both particles are 90 degrees.
But when a high-energy proton collides with a stationary proton, the angle between the two paths is not 90 degrees. Why is it so?
½ mu2 = ½ mv2 + ½ ms2
The Attempt at a Solution
I answered that it's because the collision was not elastic so the above equation couldn't apply. But the answer is that because the proton is moving near speed of light so it's mass is greater than rest mass. So is this collision between the two protons still an elastic one? How to know whether a collision is an elastic or an inelastic one by its nature? I saw on some websites they say subatomic collisions are elastic but from another past paper it says the scattering between electrons and hydrogen nuclei is an inelastic collision...