when to use relativistic versus classical energy
Posted: Thu Jul 24, 2014 8:22 pm
I think I have generally figured out when it is appropriate to use the relativistic expression for energy ($$E^{2} = (pc)^{2} + (mc^{2})^{2}$$) versus the classical ($$E=\frac{p^{2}}{2m}$$), but I want to make sure and/or learn of any other ways ETS might want us to use one or the other. I've found in general that if a question is put in terms of, for instance, MeV/c^2 it is logical to use the relativistic case, and also I've found that often the use of the word "free" (i.e. a free electron) can also suggest to use relativistic. Are there any other general times to use one or the other?