Background Information


Objects, when placed in a fluid, will either float, sink, or remain "neutral" because of the buoyant force. In other words, objects in fluid always have buoyancy that will be positive, negative, or neutral. This principle affects how an object is buoyed in water, or any other fluid.

This idea of buoyancy was perfectly defined by a Greek mathematician, Archimedes. This principle is as follows: Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. This means that the force that buoys an object is equal to the weight of the fluid that is displaced by the object when placed in the fluid. Displaced fluid is fluid that is taken away from its original surroundings. In this case, it would be the fluid that rises around the object. If the mass of the displaced water is greater then the mass of the object then the object will float. If the mass of the displaced water is less than the mass of the object, then the object will sink. If the two masses are equal, then the object will neither float nor sink, but be neutrally buoyant.

Archimedes Principle does not have a formula, and therefore many people have formed misconceptions relating to buoyancy. These are that things float because they are lightweight and that things float because of air. Neither of these situations makes something positively buoyant, as it is that the mass of the displaced fluid is greater than the object's mass that makes the object positively buoyant.
So far, when referring to Archimedes' Principle there has been a fluid in which the object that will be buoyed is placed in. When referring to diving, the fluids that are mentioned in this principle will be either salt or fresh water. A cubic foot of salt water weighs sixty-four pounds and a cubic foot of freshwater weighs sixty-two and one-fifth pounds. Therefore, salt water has a greater mass, and therefore the same object will be more buoyant in salt water because the mass of the displaced water will be greater.

Archimedes' Principle, or buoyancy, is very important to divers. It is important for a diver to obtain neutral buoyancy when diving, as it enables them to maneuver and dive more smoothly and easily. Simply, this means that it is optimal for a diver to be neutrally buoyant throughout their dive.



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