What is motion?
It is defined as displacement or movement of a body or an object from its initial position with respect to time. For example a body A can, be said to be in motion if it moves from point a to b.
Motion is perceived by different laws of physics. Among the laws Newtons laws of motion are studied in classical physics.
Newtons law of motion are categorised in three different laws.
First Law: In an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a net force.
Second Law: In an inertial reference frame, the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object: F = ma.
If the resultant force F acting on a body or an object is not equals to zero, the body will have an acceleration a which is in the same direction as the resultant.
Third Law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
Newtons law of motion
To understand the law of motion clearly, we need to understand force.
Force: it is defined as a push or pull.
To push an object like closing a door, and to pull an object like opening a door towards oneself.
Application of push or pull may not result in the opening or closing of the door. For some observers lack any motion may be inferred as lack of force but the person applying the force knows that he has put an effort. In clear terms a force is just the application of push or pull or an effort and the results are not required.