Having established F=ma , one can proceed to make further and independent discoveries. From spring-based weight measurements for various objects one finds the phydical law that an object's weight (W) is proportional to its inertial mass (m). Moreover , from projectile mption under terrestrial gravity, or from pendulum experiments a la Newton , one finds that the local gravitational field strength g is the same for all objects. This is consistent with the weight measurements when one uses a=F/m and employs g for a and W for F.