Science and Technology Intertwined: When surfers are patiently waiting for the right wave, they can allow other waves to pass beneath their boards. What are the forces at work here?

You’re sitting on your surfboard when you notice a wave approaching from behind you. Your eyes, brain, and body have all honed their timing skills so that you can catch and ride a wave when it comes along. The onrushing mass of water accelerates you as you paddle hard, and you feel the acceleration as you reach the speed of the water. After that, you maintain your balance on the board and enjoy the forces that you feel as you crank off some turns to the music. When you’ve decided to call it a day, you step back onto your board and lower the tail into the water, effectively applying the brakes.

The Pleasures of Physics

Although you didn’t need to whip out a calculator to figure out what was going to happen while surfing, there is a significant amount of physics involved in the act of riding a wave. Examine a few instances in which the laws of physics and surfing come into conflict. In the same way that a surfer starts his session, we’ll begin by waiting on the board between sets of waves. After that, we’ll look at the acceleration that occurs as the surfer catches the wave. The forces acting on the surfboard as it turns will be discussed in detail later.

Waiting for the opportunity to go

The forces of gravity and buoyancy are at work when you are lying on your board in still water, waiting for the next wave to come along: gravity pulls you down and buoyancy pulls you up. Fortunately, these forces are relatively simple to comprehend.


However, despite the fact that this force acts on every atom in you and your board, it behaves as if it were only acting at your centre of mass. When a person is standing up straight, their centre of mass is conveniently located behind their navel in the middle of their body, which is convenient for most people. Your balance point is located at your centre of mass. With the help of a support under your centre of mass, you can find your equilibrium. (For the time being, we’ll disregard the surfboard.) Of course, the board is not massless, but physicists tell these kinds of little lies all the time to help them get to the heart of a problem more quickly.


A hydrostatic force is an upward force created by still water pushing up on the board, and it is also known as a buoyant force (a force exerted by a liquid at rest). The water exerts its force on every part of the board that it touches, yet the buoyant force acts as if it were pushing up on the board just at the centre of buoyancy, which is the centre of mass of the water displaced by the board. In fact, according to legend, when Archimedes, an ancient Greek mathematician, discovered the mathematics of buoyancy while bathing, he became so excited that he leapt out of the bath and ran naked through the streets, shouting “Eureka!—I’ve found it!”

Net Force is a term that refers to a group of people who work together to achieve a common goal.

Given that you are remaining in one location, you are not accelerating. We also know that the sum of all the forces acting on you—the net force—is equal to zero, thanks to Sir Isaac Newton’s discovery. If there is no acceleration, there is no net force. Having the answer before beginning to study the physics is extremely helpful in many situations. (However, it should be noted that you can be moving at a constant velocity even when the acceleration is zero because acceleration causes changes in velocity.)