I am having trouble deciding when to use which equation.
If you're given the wavelength of a proton, let's say 100 fm, and have to find the kinetic energy of it, how would you do this?
Here are my ideas:
Idea 1: Use lambda = h/p, where p = sqrt(2Em).
Idea 2: Use E=(pc)^2+(mc^2)^2 =...