Newton’s first law in normal language: An object in motion stays in motion, or an object at rest stays at rest until an unbalanced net force acts on it. This means that if an objects is moving along, untouched by a force of any kind , it will continue to move along in a perfectly straight line at a constant speed. Newton's first law also known as low of Inertia. Inertia is tendency of an object to resist any change in its motion.

Newton’s first law: Newton’s first law states that it is possible to find an inertial frame in which an object that does not interact with other objects experiences zero acceleration, or, equivalently, in the absence of an external force, when viewed from an inertial frame, an object at rest remains at rest and an object in uniform motion in a straight line maintains that motion. Inertial frame of reference: An inertial frame of reference is a frame in which an object that does not interact with other objects experiences zero acceleration. Any frame moving with constant velocity relative to an inertial frame is also an inertial frame.