Have you ever wondered why, when we do the bathroom at seais it much easier for us to float than the swimming pool or the lake? Everything has to do with one of the most famous principles of physics, that is the Archimedes principle!
According to this principle, a body immersed in a fluid (like water) receives one upward pushed which is equivalent to the weight of the volume of the fluid that has been moved.
In other words, every time we bathe e We immerse ourselves in the water (sweet or savory), we receive one push upwards which is equivalent to the weight of the portion of water that we have moved. Based on the Archimedes principle, therefore, to ensure that a body will floats inside a fluid like water, it is sufficient for this to move a quantity of water with a weight equal to or greater than your own.
But the weight of the mass of water that is moved also depends on its own densitygiven by the relationship between mass and volume: precisely because of the presence of salt, the sea water is a lot denser Of that sweet and, therefore, with the same volume weighs much more. Specifically, if the absolute density of the water is around 0.9998 g/cm3the surface density of sea water varies between 1,020 g/cm3 and 1.027 g/dm3. So, according to the Archimedes principle, a body immersed in salted water (denser and heavier than the sweet one) will receive a higher up -to -date thrust than a body immersed in fresh water.
In short, at the sea we float more easily because thesalted waterbeing more dense than the sweet one (and therefore heavier to the same volume), it gives us a push upwards greater allowing us to make fewer efforts to stay afloat.
One of the most extreme cases of this principle is that of Dead Sea Where, in reality, swimming is very difficult due to the high salinity of the water, which causes it to float almost completely in body. In a liter of water of the dead Sea, in fact, up to 350 grams of salt are dissolved, about ten times the average world salinity.
