Part of my problem for physics is finding how far a person can move along a floating board. The board is not acted on by any outside forces so the center of mass before the person starts moving and the center of mass afterwards stays the same. Their is no air friction on the board. The Person starts on the east side. The board is 6 meters long and i know the mass of the person is 70kg and the mass of the board is 8 kg. However, the board is not uniform so its center of mass is not in the center. The person must walk westward but as he wals the board moves east. The question is how far can he move from his original position to a piece of string hanging down 5 meters to the west of him. Really need help on this problem as ive been thinking bout if for about a half hour now and its due tom. Thanks for the time and any help is appreciated.