Now, get your heads around this little dilemma
Dynamite is a tool commonly used to cut down trees. To cut a tree 18" in diameter requires five sticks of dynamite: one on the north, south, east, and west sides of the tree, and the fifth stick on the side to which the tree should fall. During construction of a dam, a tree 18" in diameter was completely covered by water. Since the tree top was fouling boat propellers, it had to be cut down. A diver went down and put a stick of dynamite on all four sides of the tree. Since the current is flowing south at 2 knots per hour, on which side of the tree would you instruct the diver to put the fifth stick of dynamite if you wanted the tree to fall north?