

Pushing water out of the way





Sitting in a hole

A simple bow wave





Climbing a mountain Archimedes' Principle tells us that a boat floats because it displaces water. The force required to push and hold the water out of the way as the boat is lowered into the water, is (by Newton's principle of equal and opposite forces) the same as the force exerted by the water to hold the boat up. However, as the boat starts to move, it has to push water out of the way. This means that the water piles up on either side of the bow (the pointy end) and that creates the bow wave that we can see so clearly as a boat travels. Not surprisingly, the faster you go, the larger the bow wave becomes. The larger bow wave in turn has a longer wave length (partly because of the boat's speed), and after a certain point the wavelength equals (or exceeds) the length of the boat. In effect, the boat has created a hole in which it sits. The deeper sitting boat now has even more water to push out of the way, and ends up having to climb a mountain of its own making.