Protons in a particle accelerator receive energy from electric fields to be accelerated to relativistic speeds. a) What is the relationship between the proton's energy and speed in this case? b) If the proton's rest mass is 0.9 Ge'u' and it is accelerated to an energy 4GUGeV, what is it's speed? c] Why is it better to use the relationship between energy and momentum, and not between energy and speed