Chapter 9, Problem 12Q

Why is it not possible to sit upright in a chair and rise to your feet without first leaning forward?

To determine

Why is it not possible to sit upright in a chair and rise to your feet without first leaning forward?

Answer to Problem 12Q

Solution:

It is not possible because the center of mass of the body is not aligned with the feet.

Explanation of Solution

Given info:

Sit upright in a chair and rise to your feet without first leaning forward.

The center of mass of the human body is aligned with the feet, the whole balance of the body depends on this alignment. When a person is sitting in a chair, his feet are displaced forward in relation to the center of mass, whereas if the person is up, his center of mass is aligned with his feet; that is, the center of mass of a person standing is just above his feet. A person sitting in a chair must obligatorily lean forward so that his center of mass is just above the feet.