It is always convenient to remember the classics. Archimedes’ principle states: ” A body totally or partially submerged in a fluid at rest receives a thrust from the bottom up equal to the weight of the volume of the fluid it displaces.”
The determining element for this push to overcome the force of gravity is density : if the object is less than the liquid, it will float. That’s why wood does it, but not lead. As in the case of water and humans are practically tied, the ability to sustain ourselves on the water surface will depend on small details.
First of all, there are sex differences . In general, men accumulate less fat and this limits their buoyancy potential. For the same reason, that is, the low presence of lipids, children and adolescents would have more problems not to sink.
And perhaps this also serves to explain, in part, why there are so few black swimmers, whose build has more bone and muscle volume than that of whites. Finally, the psychological factor must also be taken into account: a person who cannot swim and becomes nervous, may end up swallowing water and sinking due to their uncontrolled movements.
In short, your ability to float is determined by your body composition. In other words, if you are lean and muscular and have a low or even normal body fat percentage, you will most likely sink. If you have a higher percentage of body fat, then you are more than likely to float.
Why do things float on water?
Objects are made up of very small molecules. The molecules can be packed together, like in a rock or more, like in bubble wrap. The positioning of molecules affects the density of an object. Objects with very compact molecules are denser than those in which the molecules are scattered.
Density plays a big role in why some things float and others sink. Objects denser than water sink and objects less dense float.
Objects like coins, rocks, and marbles are denser than water, so they will inevitably sink. Other objects like apples, wood, and sponges are less dense than water, so they will float. Many hollow things like empty bottles, balls, and balloons will float too. This is because air is less dense than water. This is one of the reasons why large ships can float, even if they are very heavy. Inside a ship, there is a lot of hollow space filled only with air. But that’s not all: the form also matters .
The exterior of an object, the surface, is key . The more surface the water is touching, the more buoyant the object is, which means it floats better. When an object floats, it pushes the water out of the way, this is what we call displacement. But the truth is that water pushes back, so the more surface area an object has, the more water backs up against it, helping it to float. That’s another reason why even large ships don’t sink if they are shaped correctly.
Have you ever noticed that when you get into a bathtub, the water level rises? This is because your body displaces (moves) the water.
