Force and Inertia
It is external effect in the form of push or pulls which (i) produces or tries to produce motion in a body at rest, or (ii) changes or tries to change the direction of motion of the body.
It is the inherent property of a body, by virtue of which, the body cannot change its state of rest or of uniform motion along a straight line, on its own. It depends upon the mass of the body. Inertia of a body is of three types:
a) Inertia of rest b) Inertia of motion c) Inertia of direction.
i) Inertia of rest: It is inability of a body to change by itself, its state of rest. This means a body at rest remains at the rest and cannot start moving on its own.
ii) Inertia of motion: It is inability of a body to change by itself its state of uniform motion i.e. a body of uniform motion can either accelerate nor retard on its own and come to rest.
iii) Inertia of direction: It is inability of a body to change by itself its state of motion a body continues, to move along the same straight line unless compelled by some external force to change it.