Question

what is newton first law of motion

Answer 1

Newton's First Law. Newton's First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. It may be seen as a statement about inertia, that objects will remain in their state of motion unless a force acts to change the motion.

Answer 2

until and unless an unbalanced force acts on body the body remains in state of rest or state of uniform motion..
this means this property of body to resist the change of state of rest or state of uniform motion is called inertia .
and inertia is directly proportional to mass of body..