law of inertia
Physics term; refers to Newton's first law of motion. Used in scientific and educational contexts.
The law of inertia states that an object maintains its state of motion unless an external force acts upon it.
慣性 is the noun 'inertia' itself, while 慣性の法則 is the full phrase 'law of inertia'.
運動の法則 refers to Newton's laws of motion in general; 慣性の法則 is specifically the first law.
Compound of 慣性 (inertia) + の (possessive particle) + 法則 (law). 慣性 is a modern scientific term coined from kanji meaning 'accustomed' and 'nature'.