Chapter 9, Problem 9Q

Why do you tend to lean backward when carrying a heavy load in your arms?

To determine

Why do you tend to lean backward when carrying a heavy load in your arms?

Answer to Problem 9Q

Solution:

This is because the muscles of the back tend to align the center of gravity of the body with the legs to counteract the additional torque generated by heavy load.

Explanation of Solution

Given info:

The bodytends to lean backward when carrying a heavy load in their arms.

Normally, when a person is standing or walking, their center of gravity (CG)is aligned with their legs. The moment a person carries a heavy load the CG of the person is unaligned from his legs (a straight line joining the CG with the legs), this way due to the heavy load an additional torque is generated that tends to move the body forward. To counteract this additional torque and prevent the person from falling forward, the muscles of the body, especially those of the back, tend to move the spine backwards to achieve equilibrium. It is for this reason that you tend to lean backwards when you carry a heavy load in your arms.