Chapter 11, Problem 13A

In terms of center of gravity, support base, and torque, why can you not stand with your heels and back to a wall and then bend over to touch your toes and return to your stand-up position?

To determine

To explain: The reason for not standing with heels along with back to a wall and then bend over to touch the toes.

Answer to Problem 13A

A person cannot stand with heels back to a wall because the vertical line through the centre of gravity does not pass through the base of the persons support, since the torque acts on the person.

Explanation of Solution

Introduction:

The centre of gravity of a body is the point where all the forces that are acting on a body will be equal to zero.

When a person is standing against a wall, the centre of gravity, that is acting vertically downward, lies within the area covered by feet and the base support. So, when a person lean forward, the body will be adjusted due to centre of gravity. But when a person is standing against a wall, the body cannot adjust itself within the base, since the centre of gravity acts in the backward motion that is restricted by the wall. Therefore, when a person tries to lean forward, the centre of gravity will be shifted to the base, so that they will tend to fall since the torque acts on the person.