Chapter 9 - Static Equilibrium; Elasticity and Fracture - Search and Learn - Page 259: 1

For you to remain balanced, your center of mass must be above your base of support on the floor. When you are flat-footed on the floor, your center of mass is above your feet. When you go up onto your tiptoes, your center of mass attempts to move forward so that it will be above your toes. However, due to your finite width and the fact that you cannot move your body inside the wall, your center of mass cannot move forward to be above your toes. You cannot balance on your tiptoes next to the wall. If you turn around and place your heels several inches away from the wall, you could lean back and push against the wall. In this case, your center of mass would be above a point between your feet and the wall. Your feet would create a torque that would rotate your back toward the wall. To prevent from falling over, you would need the normal force of the wall pushing against your back. When your heels are placed against the wall, it is not possible for your center of mass to be between your feet and the wall. Your back therefore cannot push against the wall in this position.

For you to remain balanced, your center of mass must be above your base of support on the floor. When you are flat-footed on the floor, your center of mass is above your feet. When you go up onto your tiptoes, your center of mass attempts to move forward so that it will be above your toes. However, due to your finite width and the fact that you cannot move your body inside the wall, your center of mass cannot move forward to be above your toes. You cannot balance on your tiptoes next to the wall. If you turn around and place your heels several inches away from the wall, you could lean back and push against the wall. In this case, your center of mass would be above a point between your feet and the wall. Your feet would create a torque that would rotate your back toward the wall. To prevent from falling over, you would need the normal force of the wall pushing against your back. When your heels are placed against the wall, it is not possible for your center of mass to be between your feet and the wall. Your back therefore cannot push against the wall in this position.