Final answer:
In Physics, specifically within the context of rotational motion and equilibrium, solving a problem involving a pivot often pertains to High School level content. To see the back of your head using mirrors, a minimum of two mirrors are necessary, which demonstrates the physics of reflection.
Step-by-step explanation:
The question refers to solving an example problem by choosing the pivot at the location of the rear axle, which is related to the physical concepts of rotational motion and equilibrium. This falls under the subject of Physics. The question seems appropriate for High School grade level, typically dealing with introductory mechanics.
In understanding the mechanism of mirrors according to Physics, specifically optics, to see the back of one's head, a configuration of mirrors is required. The minimum number of mirrors needed to see the back of your own head would be two. By placing one mirror in front of you and the second mirror behind you, angled in such a way that reflects the image from the first mirror to your eyes, you can see the back of your head. This setup uses the law of reflection, where the angle of incidence equals the angle of reflection.