I have read the equation F = ma "does not apply directly on the very small scale of the atom where quantum mechanics must be used." What exactly is therefore used instead of F= ma? Furthermore, would it be possible (if we ignore the complexity of them) to use these quantum calculations to work out macro effect? eg - the acceleration a 1kg mass would udergo if pushed by a 45N force? Does this therefore mean that the quantum calculation is the more "correct" way and that F=ma just happens also to work for things on a large scale? Thanks in advance.