Any 'physical' quantity is expressed as (generally) a Real Number. Real Numbers are abstract mathematical constructs.
Laws of Physics are written as mathematical equations; where these real numbers are equated to each other (By now we have already left the world of physics and are purely in mathematics)
But when we 'measure' any physical quantity we can only measure up to a level of precision. (And this is due to resolution of the measurement instrument - I'm not talking of quantum effects etc.)
Say for e.g. distance ($d$), speed ($s$) and time ($t$) $d = s*t$ (I know this is a definition and not a law but explains the point try to make here)
But when I measure $s$, $d$ and $t$ and plug those values in - I will never get an equality only an approximation.
I will never know (i.e. measure) what is the value of real number $d$ which represents distance for me (and similarly for any other physical quantities). If I can never know $d$ - What's the point of putting them in equations?
Does this put some fundamental limitation?
Apologies if I'm unable to frame my question well - even I'm not very clear on what am I finding difficult to grasp. Any pointers would be helpful please