top of page

Physics - Newton’s First Law of Motion

Definition of Inertia and Mass

Inertia is the natural tendency of an object to remain at rest or in motion at a constant velocity. The mass of an object is a quantitative measure of inertia

SI Unit of Inertia and Mass: kilogram (Kg)


Inertia plays a central role in one seat-belt mechanism. The grey part of the drawing applies when the car is at rest or moving at a constant velocity. The coloured parts show what happens when the car suddenly slows down, as in an accident.


bottom of page