Wednesday, January 13, 2010
Physics of Surfing
How do surfers ride big ocean waves?
1) Ocean waves are a form of mechanical waves. Mechanical waves are disturbances traveling through space and time which jump from one particle of the medium (in this case water) to another ... so mechanical waves move energy, not physical substance. Wind causes ocean waves travel along the surface of water. Slope and width of ocean bed and wind speed, duration, and size all effect ocean waves size.
2)OK, so now that we know what ocean waves are, how do you surf them? Newton's 1st law states that, minus an outside force, objects in motion (e.g. waves) stay in motion and objects at rest (e.g. surfboards) stay at rest. Newton's 3rd law states every action has an equal and opposite reaction. As waves rise, they reach a point where they cannot sustain themselves and begin to collapse. This point of collapse is known as the wave's "break". Surfers exploit the break, pushing down on the board as the wave pushes up on the board. The board does not sink because the ocean water is denser than the surfboard. Also, water surface tension (the force which allows water to stick together and form droplets instead of spread out) is very strong and helps push the board up. All that's left is for the surfer to maintain their center of gravity, much like one does when riding a bicycle.
Now that you know all that, see if this doesn't seem to defy wave physics.