Question

what is first law of motion

Answer 1

Newton's first law of motion is often stated as

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...
Newton's first law of motion is also known as law of inertia

Answer 2

An object remains in a state of rest or of uniform motion in a straight line unless acted upon by an external unbalanced force.