Inertia is a tendency to do nothing or to remain unchanged.
It is a property of matter by which it continues in its existing state of rest or uniform motion in a straight line unless that state is changed by an external force.
Inertia is the <u>resistance to a change in motion</u>.
Therefore, an object at rest remains at rest and an object in motion remains in motion <u>with the same velocity</u> unless acted upon by an unbalanced/external force.
