Here the quantity m (the inertial m

Here the quantity m (the inertial mass) is a property of the object under study; thus , once the proportionnality is established by measuring (F) (in newtons, say , using , e.g. , a spring and Hooke's law) and (a) (in, say , m/s) , the proportionality constant 1/m can be determined. This view is similar yo that taken when establishing Ohm's law, where the current (I) is proportional to the voltage difference (v) for small enought (v) that nonlinear effects do not appear) , with 1/R being the proportionality constant : I=v/r . Just as determination of R once and for all permits one to relate other values of voltage difference and current, so determination of (m) once and for all permits one to relate other values of force and acceleration.