Why do objects keep moving after the force stops acting on it

It keeps moving for just a few seconds because of inertia. Say you are going 50 miles down the interstate there is a stop sign when you stop you almost come out of your set that is why we have to wear set belts and that is an example of Inertia. Glad to help

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.