The Physics of Surfing

While there are some aspects of surfing that have to do with concepts of physics beyond this class, there are still a number that are relevant to what we have learned, including fluids, kinematics, and torque:

1. When waiting for a wave to come, you are floating on the board. This is possible as a result of buoyant force pushing up on the board and opposing the force of gravity acting on you and the board.

2. When you turn and begin to paddle to catch a wave, you are accelerating yourself (and the board) from rest to match the speed of the wave you are trying to catch.

3. Balance and turning: When you are balanced on the surfboard, the downward force of gravity and the upward force of buoyancy are in line. If you shift your weight relative to the center of mass of the board, those two forces are no longer in line, and the board will experience a torque. If you were to move backward, for example, the nose begins to go up and the tail begins to go down. This changes the position of the buoyant force, so the board will rotate until the opposing forces of buoyancy and gravity are in line again. Depending on where you shift your weight, you can tip the nose up or down, and the left or right side down. This shifting and torque, when applied deliberately, can allow you to turn the board.

4. When the wave is forming, the particles of water at the top—at the crest of the wave—are actually moving faster than the particles in the wave itself; they have a greater acceleration. These particles move forward and end up ahead of the rest of the wave. It is the downward force of gravity on these particles that causes the characteristic curl of a wave.

As a final, semi-related side note, the waves experienced on the beaches of California may be coming from as far away as New Zealand, which is really far.