Question

What is the difference between inertia and Newton's first law of motion?

Answer 1

There is no difference. The term inertia is introduced using Newton's First Law of Motion.

Newton's first law of motion states that "An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." ... This tendency to resist changes in their state of motion is described as inertia.