Sex reassignment surgery for male-to-female involves reshaping the male genitals into a form with the appearance of, and, as far as possible, the function of female genitalia. Prior to any surgeries, patients usually undergo hormone replacement therapy (HRT), and, depending on the age at which HRT begins, facial hair removal. There are associated surgeries patients may elect to, including facial feminization surgery, breast augmentation, and various other procedures.
The answer is force because Force is needed to change the direction of a moving mass.
Men naturally have more muscle mass than women and thus need more energy to function
