3. A new physical law: Proportionality of weight and inertial mass
In what follows we solely consider terrestrial gravity. We assume that the law of universal gravitation has not yet been discoveres.
A.Kinematics measurements (rules and clocks) establish the law of fall
Our hypothetical scientist can measure velocities and accelerations (no matter the cause of the acceleration) to a part in 1044. They now consider accelerations solely caused by terrestrial gravity. Such use of rules and clocks yields, when air resistance can be neglected (as in Boyle's experiments using an evacuated chamber), that to a part in 1044 all objects fall under gravity with the same local acceleration |a|=g (which can depend on locale), Similar conclusions can be
made for pendulum motion using clock alone, if the mass distributions and pendulum lengths are the same. If Newton's second law is assumed to be correct, and if the force of gravity is taken to be the weight W, then we conclude that g=W/m is the same for all objects: the weight is proportional to the mass.