Resultant force, mass and acceleration are linked by F = ma. At constant mass, acceleration is proportional to resultant force; at constant force, larger mass gives smaller acceleration. Inertial mass measures resistance to acceleration and is the ratio of resultant force to acceleration. Example: A 4 kg object has 20 N driving force and 8 N resistance. Calculate acceleration. Resultant = 20 − 8 = 12 N; a = F/m = 12/4 = 3 m/s² in the driving direction. Use clear labels. Avoid unjustified claims.