Chapter 7, Problem 17Q

To determine

To draw: A diagram showing the shifting of centre of mass.

Answer to Problem 17Q

Centre of mass shifts from the centre of the body to some distance ahead from his stomach in sitting position.

Explanation of Solution

Introduction:

The centre of mass is defined as a unique point in any object at which the summation of weighted relative position of the distributed mass is zero.

Consider the figure shown below.

  

In the lying position, the centre of mass is in the middle of the body, somewhere near the stomach. Because in the lying position, all the mass is in horizontal direction. So, calculated center of mass comes in the middle of the body.

But, in the sitting position, centre of mass shifts ahead of the stomach that is somewhere in the air but inside the body. Because, in the sitting position, mass is distributed in horizontal and vertical position, Thus, the center of symmetry taken for both axis gives the point nearly outside of the body.

Conclusion:

Thus, the centre of mass shifts from the middle of the body in lying position to somewhere ahead of the stomach or the middle position.