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 mentioned “in all probability” as a result of I do not need to choose 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 may be much less air above you pushing down. In that case, ship me an image.) By way of pressure and space, it is the same as 100,000 newtons per sq. meter.

Water can also be fabricated from tiny shifting molecules that act like balls, and people molecules collide with underwater objects (like individuals), 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 identical 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 ft) under 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 bigger the deeper you go, the water beneath pushes up greater than the water above it pushes down. This distinction compensates for the downward gravitational pressure, so the water degree stays fixed.)

It would sound like 43.5 psi is an excessive amount of for an individual to deal with, but it surely’s really not that dangerous. Human our bodies are very adaptable to modifications in stress. When you’ve got been to the underside of a swimming pool, you already know the reply to this stress drawback—your ears. If the water stress on the skin of your eardrum is bigger than the stress from the air inside your interior ear, the membrane will stretch, and it will possibly actually damage. However there’s a good trick to repair this: Should 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 interior 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 really one other air area that it’s essential 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 might 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 could have the identical lung quantity, and so they include the identical quantity of air. Nonetheless, the water stress exterior of them will lower. The decreased exterior stress in your lungs makes it as if they’re overinflated. This will trigger tears in lung tissue, and even pressure air into the bloodstream, which is formally dangerous stuff.


There’s one other drawback to cope with when you’re underwater: floating and sinking. If you wish to keep underwater, it’s helpful to sink as an alternative of float—to some extent. I do not assume anybody needs to sink to such depths that they by no means return. Additionally, it’s good to have the ability to float while 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 pressure is bigger than the upward-pushing buoyancy pressure. If these two forces are equal, then the article will likely be neutrally buoyant and neither rise nor sink. It is like hovering, however in water, and it’s primarily what you need to do when scuba diving.

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