Newton’s first law includes: (i) the definition of inertia (ii) the definition of force (iii) both (a) and (b) (iv) none of the above

both (a) and (b)

Reason — Newton’s first law can be understood in two parts:

1. Definition of inertia — In the first part, Newton’s first law gives the definition of inertia, according to which an object cannot change its state by itself. If the object is in state of rest, it will remain in the state of rest and if it is moving it will continue to move with same speed and in same direction, unless an external force is applied.
2. Definition of force — The second part of Newton’s first law defines force, according to which force is that external cause which can move a stationary object or which can change the state of motion of a moving object.