When a mixture of different substances is rotated at extremely high speeds within a closed path (in your case a closed container), substances of higher mass often go on to the outermost path and lighter particles experience the nearest to rotating axis. The same principle can be used in centrifuge oil cleaning. Birth Control Patch works on the foundation of hormones. Basically it has two female hormones estrogen and progesterone, which prevents ovulation. It does not permit the eggs to developing from your ovaries. So, if there is no egg, what sperm will fertilize, knowning that prevents pregnancy. It also thickens the cervical mucus in order that the sperm cannot achieve the eggs.