Ever wondered why a small metal coin sinks and a big ship doesn’t?
Oh, it’s all based on the concept of density. And the whole idea of density comes from the concept of the Archimedes principle. It is because of this principle we know why big ships float on the water, and do not sink.
So, what is the Archimedes principle?
Archimedes’ principle, physical law of buoyancy, discovered by the ancient Greek mathematician and inventor Archimedes, stating that any body completely or partially submerged in a fluid (gas or liquid) at rest is acted upon by an upward, or buoyant, force, the magnitude of which is equal to the weight of the fluid displaced by the body.
What is density?
Density is a measure of mass per volume. The average density of an object equals its total mass divided by its total volume. An object made from a comparatively dense material (such as iron) will have less volume than an object of equal mass made from some less dense substance (such as water).
FLOATATION:
When a body of density ρ and volume V is completely immersed in a liquid of density, the following two forces act on the body:
1. Weight of body, W=Vρg acting vertically through the center of the gravity.
2. Buoyant force or upward thrust, FB = V*liquid density*g equal to the weight of the liquid displaced, acting vertically upwards through the center of the buoyancy.
So, in simple words we can define the Archimedes principle as: when a body is wholly or partially submerged in a liquid, buoyant force acts on it thus reducing the weight of the object which is equal to the weight of the liquid displaced.
Depending upon these formulas, there are three cases:
- W > FB , the body will sink to the bottom of the liquid. This happens when the density of solid is greater than the density of the liquid.
2. W < FB , the body will rise above the surface of the liquid to such an extent that the weight of the liquid displaced by the immersed part of the body ( i.e. upward thrust ) becomes equal to the weight of the body. The body will then float. In this case, the density of the body is lesser than the density of the liquid.
3. W = FB , the body is at rest anywhere in the liquid. The body will float if its whole volume is just immersed in the liquid. In this case the density of the body is equal to the density of liquid.
Therefore from the above conditions, we now know why big ships float. This is because of density. The density of the ship is much lesser or equal to that of the water.
Thank you!