Answer to Question #134337 in Electricity and Magnetism for Vinayak sharma

Question

A policeman directing traffic is standing upright with his arms down at his side. He motions traffic by raising his arms to horizontal and pointing to the left with both arms perfectly straight at shoulder height. His overall center of gravity has been:

1. Raised and shifted right

2. Lowered and shifted right

3. Raised and shifted left

4. Lowered and shifted left

Answer 1

Imagine that you have a body and two masses almost independent from the body - two arms. When the arms are down in their usual position, the body has a fixed centre of the mass. If you are rising your arms up, mass distribution will change, now upper part of the body is heavier than before. To maintain balance, centre of the mass will move up respectively. The same is true in any direction. If the arms have moved up and left, centre of the mass shifts up and left as well.

Answer: 3. Raised and shifted left