So what you're saying is that it only applies (in the exact lambda=h/p) for relativistic particles? (as its the only time where you can neglect mc^2).
Because in many examples in textbooks it applies the formula to non-relativistic conditions.
That E does not equal cp, it equals the square root of (cp)^2 + (mc^2)^2. So for de broglie equation, you have to neglect mc^2, which I can see as reasonable if it is very small in comparison to cp, but there are many occasions where it won't be.
de broglie combines E=hc/lambda and E=cp...
OK so you get to the matter wave equation 'lambda = h / p' using E=cp - which describes the energy for massless particles. I can understand this holding for when cp>>mc^2 , but not for when the mc^2 is comparible. Any help?
But if the chemical composition changes, then the question has no value because the coeffecient of friction is between the two surfaces, and a surface has changed. ie. all you would be saying is that the kinetic friction is higher between these two surfaces than the static friction between these...