Suppose you are myopic (nearsighted). you can clearly focus on objects that are as far away as 52.5 cm away. you can clearly focus on objects which are as close as 17.2 cm from your eyes, but no closer. the purpose of glasses would be to make objects that are far away appear to be at your far point. what would be the refractive power (in diopters - do not enter units) for your prescription? if your glasses make distant objects appear to be at your far point, then any object that is closer to you will appear even closer than it really is. what is the closest distance from your face at which you could hold a book and still be able to see it clearly while wearing your glasses?

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.