The Physics of Scuba Diving



One other unit is the bar, the place 1 bar is the same as 14.5 psi. The worth of 1 bar may be very near the stress of air on Earth. The atmospheric stress of the air that surrounds you proper now might be 14.5 psi. (Sure, I stated “in all probability” as a result of I do not wish to decide you. Possibly you might be studying this from the highest of Mount Everest, the place the stress is simply 4.9 psi, as a result of there’s much less air above you pushing down. In that case, ship me an image.) By way of drive and space, it is the same as 100,000 newtons per sq. meter.

Water can be made from tiny shifting molecules that act like balls, and people molecules collide with underwater objects (like folks), producing stress. Water has many extra molecules than the identical quantity of air, which suggests there are extra collisions to provide a better stress. However similar to going to the highest of Mount Everest decreases the air stress, going deeper in water will increase the stress, as a result of gravity pulls downward on the molecules of water. For each 10 meters of depth, the stress will increase by 1 bar, or 14.5 psi. That implies that on a dive 20 meters (round 60 toes) beneath sea degree, there can be a water stress of 43.5 psi, thrice better than the air stress at Earth’s floor.

(The truth that stress will increase with depth prevents all of the ocean’s water from collapsing into an infinitely skinny layer. For the reason that stress is larger the deeper you go, the water beneath pushes up greater than the water above it pushes down. This distinction compensates for the downward gravitational drive, so the water degree stays fixed.)

It would sound like 43.5 psi is an excessive amount of for an individual to deal with, however it’s truly not that dangerous. Human our bodies are very adaptable to modifications in stress. When you have been to the underside of a swimming pool, you already know the reply to this stress downside—your ears. If the water stress on the surface of your eardrum is larger than the stress from the air inside your inside ear, the membrane will stretch, and it could actually actually damage. However there’s a good trick to repair this: When you push air into your center ear cavity by pinching your nostril closed whereas trying to blow air out of it, air will likely be pressured into this cavity. With extra air within the inside ear, the stress on each side of the membrane will likely be equal and you’ll really feel regular. That is referred to as “equalization,” for hopefully apparent causes.

There’s truly one other air area that you’ll want to equalize whereas diving—the within of your scuba masks. Remember so as to add air to it as you go deeper, or that factor will awkwardly squish your face.

There may be one different physics mistake a diver may make. It is potential to create an enclosed air area in your lungs by holding your breath. Suppose you maintain your breath at a depth of 20 meters after which transfer as much as a depth of 10 meters. The stress inside your lungs will keep the identical throughout this ascent, as a result of you’ve the identical lung quantity, and so they comprise the identical quantity of air. Nonetheless, the water stress exterior of them will lower. The lowered exterior stress in your lungs makes it as if they’re overinflated. This may trigger tears in lung tissue, and even drive air into the bloodstream, which is formally dangerous stuff.


There’s one other downside to cope with when you’re underwater: floating and sinking. If you wish to keep underwater, it’s helpful to sink as a substitute of float—to a degree. I do not suppose anybody needs to sink to such depths that they by no means return. Additionally, it’s good to have the ability to float if you’re on the floor. Fortunately, scuba divers can change their “floatiness” for various conditions. That is referred to as buoyancy management.

Issues sink when the downward-pulling gravitational drive is larger than the upward-pushing buoyancy drive. If these two forces are equal, then the thing will likely be neutrally buoyant and neither rise nor sink. It is like hovering, however in water, and it’s primarily what you wish to do when scuba diving.

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