Inertia refers to a body or any physical object’s resistance to a change in motion. This change in motion includes, speed, direction, or state of rest. Objects that have moved will keep moving in a straight line at constant velocity. Inertia is one of the fundamental principles of classical physics, for it describes motions of objects and how they are affected when forces are applied on them. Inertia is one of Isaac Newton laws from Philosophia Naturalis Principia Mathematica.