Answer:
Principle of law of inertia
Step-by-step explanation:
According to the law of inertia, an object that stays at rest tends to remain at rest or in motion until an exterior force is applied to it. This law initially was the basic supposition of classical mechanics that later helped in understanding how the object moves, the factors that generally affect this motion and what are the applied forces and how they influence them.
This inertia is generally concealed by the gravitational force and both the effects of air resistance as well as frictional force causes a gradual decrease in the velocity of the moving object.