As you know, the noun 'biology' forms the adjective 'biological', and 'chemistry' forms 'chemical'. What is the adjective formed from the noun 'physics'? (It can't be physical, as this has other meanings e.g. tangible, related to real, not imaginary or metaphysical things).
Actually, physical is the word you're looking for. I know it seems strange, because physical meaning "tangible" or "doctor's exam" is much more common, but look at this fourth definition from dictionary.com:
pertaining to the physical sciences, especially physics
Or this third definition from Oxford Dictionaries:
Relating to physics or the operation of natural forces generally
They even share the same origin (as we can see here); both terms derive from the Latin word physica, "the study of nature". So while it may seem cumbersome, these words are just homonyms. If possible, you can also use words for subfields in physics, like quantum, mechanical, molecular, nuclear, and more.
Hope I could help.
In many cases, as it pertains to the science of physics, you can use physical as the corresponding adjetive. For example, you can say that water evaporation at 100 oC is a physical process, not a chemical process. Another example: Size is a physical property of an object.