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Buoyancy

Do you know when we fall from a boat then what will happen to our body; yes, we know that we would be sinking in water. This explanation is given by Archimedes' principle. The principle of Archimedes gives a complete description about the cause of floating or sink of objects. He explains us that what will happen to our body. He found that water pushes in the upward direction opposite to object and this force is equal to the weight of displaced water.

When an object is in the water then it displaces some amount of water according to its weight. The amount of displaced water is calculated by object’s density which relates to volume. The volume of a cricket ball and beach ball can be same their different weight their density is differed. The steel solid block sinks in water but the steel ship does not. Thus the amount of displaced water in the upward direction is explained in terms of Buoyancy force. Let’s discuss about the buoyancy force and its formulation with its different devices based on it.

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What is Buoyancy?

Why do you think the crown in water feels lighter than it actually is? When we immerse the body in a fluid, an upward force is experienced by the body. This force is exerted by the fluid on the body which makes it to rise up and is called the Force of Buoyancy.
The magnitude of this force is exactly equal to the amount or weight of the liquid displaced.

Buoyancy Definition

The upward force experienced by the fluid on the body or the object when an object is inserted or immersed in the fluid is called Buoyancy.
The point where the force of Buoyancy is exerted or the point on the body where the force acts is called the Center of Buoyancy.It should be noted that the force of buoyancy is a vertical force and hence the Center of Buoyancy is the point located on the center of the gravity of the liquid that is being actually displaced by the object immersed.

Buoyancy Force

If we consider a single column of liquid then it can be considered as the mixture of many overlying layers, one over the other with varying pressure. The pressure at the bottom of the liquid would be greater than at the top, this is because as we go down in the liquid the number of overlying layers of the liquid - the layers one over other, increases.
Due to the difference in the pressure between the layers, there tends to be an imaginary force acting in the upward direction. This force leads to the acceleration of the object, that has been immersed, in the upward direction. The force isalwaysin vertical direction.
We can also say that the magnitude of the upward force is basically equal to the difference in the pressure of the top and the last layer and also equal to the weight of the liquid that has been displaced.
Floating is the result of the above concept. The material should be less dense than water, otherwise, if its density is greater, it will tend to sink.

For Example:

If we have a rock which is hanging on the thread in a pool and initially a force of 20 Newton is exerted by it.
Now the force of buoyancy exerted back by water is 3 Newton,
Then the Net force exerted by the rock is 20 â€“ 3 = 17 Newton.

It is quite easy to pull object through water then to actually lift them from the bottom of water pool. Buoyancy is identical to the Water Displacement Method.

Buoyancy Formula

The formula for buoyant force is:
Fb = P A = g $\rho$ V = $\rho$ g h A ..........................(a)
Here, P = pressure
Fb = force of buoyancy in Newton,
A = Area in meter square,
g = acceleration due to gravity,
h = Height at which force acts taken from the surface,
$\rho$ = density of the fluid,
V = volume of the object inserted into the fluid.
Also,
Fb = Wa – Wf .....................(b)Where, Fb is the buoyant force
Wa = The Normal weight of the object when it is in air,
Wf = The Apparent weight of the object when it is in the immersed in the fluid.
Hence using (a) in (b)
g $\rho$ V = Wa – Wf ..........................(c)So volume or
V = $\frac{W_{a} – W_{f}}{g \rho}$ .................(d)
And putting it in the formula for density we get:
$\rho$ = $\frac{W_{a} – W_{f}}{gV}$ ..........................(e)
If the object is not sinking then Fg = Fb
mg = $\rho$ v g .......................................(f)where, Fg = Force under gravity

Astral Buoyancy

Astral Buoyancy provides life jackets for river rowers and gliders. This jacket maintains the condition of positive buoyancy and hence prevents them from drowning. These jackets basically create such a density die to the air in them such that the total density of the person with the jacket is less than that of water and hence the person does not sink.

Neutral Buoyancy

Neutral Buoyancy is a situation in which the body immersed in the fluid will just float. It will neither rise nor sink.
The object’s physical weight will balance with the weight of the liquid it displaces.

Example
:
In scuba diving it is very important to maintain the state of neutral buoyancy. This is done by controlled breathing. The concept of life jackets originated from here.
Today this concept is applied to reduce the density of various devices so that they can float.

Applications:
This concept is useful for scuba drivers, engineers as it assists them with technology to make submarines, boats etc. It is also useful to train astronauts for the mock conditions of microgravity.

When the condition of neutral buoyancy takes place then the object seems to be in the middle that is in between the surface and the bottom.