How Does a Pool Noodle Stay Afloat?
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Buoyancy
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Have you ever wondered how something as simple as a foam pool noodle can not only stay afloat, but support a person, as well? All floating objects are able to rest on the surface of the water because of a scientific concept known as "buoyancy." This includes objects made of materials that would normally sink, like boats made of metal.
The basic principle of buoyancy is that even though gravity pulls an object down, objects can float because water exerts its own pressure on anything within it. A pool noodle floats, essentially, because the water pushes it up.
Shape and Displacement
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While water will put pressure on any object within it, not all objects will float. Whether an object has the buoyancy to float is based on how much water it displaces, or pushes aside, in order to make room for itself. In order to float, an object has to be shaped in such a way that it displaces enough water to be at least equal to its own weight, and it must displace this much water before it becomes fully submerged.
This is possible because displacement is not based on an object's weight, but its density. A solid ball of plastic is denser than water, so it will sink because per square inch, it puts more pressure on the water than the water puts on it. However, if that plastic is used to make a container full of air, such as a boat or foam with thousands of little air pockets, it has a density closer to that of air and much lower than that of water. A pool noodle has a low enough density that it can support not only its own weight, but the weight of a person in water (human bodies do float in water on their own, but they need some support in order to float face up). -
Holes and Weight
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The difference between a boat and foam is that when a boat has a hole in it, it will sink. This is because the hole causes the boat to fill up with water, causing it to sink because it is no longer less dense. Pool noodles, on the other hand, can resist filling with water because they are made with either a form of foam that has its air pockets sealed off, or foam with very small air pockets that make water penetration difficult.
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- Photo Credit Wikimedia Commons
