What is the answer to this problem?

Question

why do you tend to lean backward when carrying a heavy load in your Arms?

Answer 1

It's balance. If you were to have a heavy weight in your arms and not lean back you would fall forward. While this may be funny, it is not suggested so most people lean back to prevent a painful and embarrassing experience

Answer 2

This is meant to balance your center of gravity that way you don't fall. Its the same idea as leaning to your left if you carry heavy items in your right arm. Balance is the main idea.

Answer 3

With the carrying of the books you change your center of gravity since the added mass is in your outstretched arms thus you have to compensate (or balance it out) - so you don't fall over. Which both of the first two posters are stating the same but they got their first.