I overheard my daughter one day telling her siblings that she atimes hate the way things are done, "Men have to learn before Swimming, but ship, as big as it is just gets in water and floats!!" I almost laughed out my intestine. That was about 10 years ago. So, in the case of people that their kids are saying the same, I bring to you; Equilibrium Of Forces.
Equilibrium of Forces is the situation where two or more forces acting on a body are exactly balanced.
Types of Equilibrium of Forces.
Stable Equilibrium:
The rocks aren't falling because the force acting on them tends to pull it to the position which it stands, thus, a slight push may not make it to fall.
Unstable Equilibrium
A boy standing in the rope might be stable, when the rope is moved, then the boy will stagger and loose balance. Here, there's no force tending to pull the boy back to his position.
Neutral Equilibrium
A log of wood lying on its side when moved slightly rolls over to a new position very similar to the old one, but doesn't fall. Here, there's no force acting on the log tending to pull it back into its original position.
Equilibrium of Bodies in Liquid
If the density of a body is less than the of a liquid, the body, if completely immersed in that liquid experiences an upward thrust more than its weight. If the density of a body is equal to the density of a liquid, the body will remain in equilibrium anywhere within the liquid. If the density of a body is greater than the density of a liquid, the body will sink. This implies that the weight of a body has its role to play in the floating and sinking of a body in a liquid.
Hence, a body displaces the weight of the fluid on which it floats.
Note:
If W<U, object comes up
W=U, object floats
W>U, objects sink.
Upthrust
It is an upward force exerted by a liquid to a body immersed in it.
Application Of Upthrust
Ship.
Ship floats in water despite the material used in making them; Iron and Steel.
Floating of ship is possible because there's a hollow or the ship floor is like an empty box. The air trapped in this hollow makes the ship lighter than the water it is immersed in.
The ship sinks to the level such that the upthrust is equal to the total weight of the ship. If it sinks too low with a cargo, the ship will sink. A ship has a line painted on its hull which must be above the water. These lines are called plimsolls lines.
Submarine
It floats with its conning tower. It has a large ballast tank which may be filled with water. The buoyancy of a submarine depends on the quantity of water in its ballast tank. When it is required to dive downwards, water is let in to the ballast tank. But when water is ejected from the ballast tank, the submarine rises to the surface and floats just like any other ship.
Archimede's Principle
It states that, when a body is immersed completely or partially in a liquid, it displays an upthrust which is equal to the weight of the liquid displaced by it.
That's all I have for Equilibrium Of Forces.