Where the different rules of physics apply:
Regular, otherwise known as Newtonian physics only applies on the average, everyday, scale. That is, objects larger than an atom at low energy, where energy in this context refers to velocity and (sometimes) temperature.
Once you step it up, increasing to high energy levels, (when velocity approaches c, the speed of light) newtonian physics no longer works due do what we call relativity, and observations or calculations need to take into account this effect usually using some form of the Lorentz factor,
gamma = [ 1 - (v^2)/(c^2) ]^(-1/2)
On the other hand, if you keep to a low energy system but bring the scale down to sub-atomic particles, such as electrons, things change yet again, but this time in an entirely new way. This is where Wave-Particle dualtity theory comes into play, the theory that waves (namely electromagnetic, i.e. light) are particles, and particles are wave packets. not only do you need to account for this, but you also need to take into account Heisenbergs uncertainty principle; It is impossible to know both the exact velocity and exact position of a sub atomic particle, the more certain you make one the less certain the other becomes.
Finally we come to Quantum Field Theory, which i honestly do not know anything about, at least i won’t until third year physics when i start taking courses on it.
This is a brilliant way to explain the different disciplines.
In the class I’m teaching, we will be working in the lower right quadrant of that graph where energies are (relatively speaking) rather low, however the scale (from a quantum point of view) is really rather large.
One could apply many of the approaches used in other sub-fields. For instance, you could calculate the mass of an object by using the multi-part mass calculation from nuclear physics, except summing up every nucleus within the object.
This is, however, a bit cumbersome and time-consuming, so we often don’t do it. The only time we run into issues is if we attempt to use Newtonian physics to explain quantum effects (as it has nothing in its framework to account for things like magnetic spin, Pauli exclusion principle, etc.)
Just remember, everything is connected.