what make ships float?

Answer 1

buoyancy is an upward force on an object immersed in a fluid (i.e., a liquid or a gas), enabling it to float or at least to appear lighter. Buoyancy is important for many vehicles such as boats, ships, balloons, and airships.
Buoyancy provides an upward force on the object. The magnitude of this force is equal to the weight of the displaced fluid. (Displacement is the term used for the weight of the displaced fluid and, thus, is an equivalent term to buoyancy.) The buoyancy of an object depends, therefore, only upon two factors: the object's volume, and the density of the surrounding fluid. The greater the object's volume, the higher the buoyancy. The higher the surrounding density, the greater the buoyancy.

It should go without saying that if the buoyancy of an (unrestrained and unpowered) object exceeds its weight, it will tend to rise. And an object whose weight exceeds its buoyancy will tend to sink.

The atmosphere's density depends upon altitude. As an airship rises in the atmosphere, therefore, its buoyancy reduces as the density of the surrounding air reduces. The density of water is essentially constant: As a submarine expels water from its buoyancy tanks (by pumping them full of air) it rises because its buoyancy stays the same (because volume of water it displaces stays the same) while its weight is decreased.

As a floating object rises or falls the forces external to it change and, as all objects are compressible to some extent or another, so will the object's volume. Buoyancy depends on volume and so an object's buoyancy reduces if it is compressed and increases if it expands.

If an object's compressibility is less than that of the surrounding fluid, it is in stable equilibrium and will, indeed, remain at rest, but if its compressibility is greater, its equilibrium is unstable, and it will rise and expand on the slightest upward perturbation, or fall and compress on the slightest downward perturbation.

The depth of a submarine tends to be unstable. A submarine is more compressible than the surrounding water. As depth increases, the resulting pressure causes the submarine's volume to decrease more than the volume of the surrounding water decreases. Buoyancy depends upon the object's volume and the weight of the displaced fluid. Volume has decreased so the the weight displaced has decreased which means a decrease in buoyancy and the submarine tends to sink further. A rising submarine expands more than the surrounding water, the submarine tends to rise further.

The height of a balloon tends to be stable. As a balloon rises it will tend to increase in volume with reducing atmospheric pressure. But the balloon's cargo will not expand. The average density of the balloon decreases less, therefore, than that of the surrounding air. The balloon's buoyancy reduces because the weight of the displaced air is reduced. A rising balloon tends to stop rising. Similarly a sinking balloon tends to stop sinking.

It was the ancient Greek, Archimedes of Syracuse, who first discovered the law of buoyancy, sometimes called Archimedes's principle:

The buoyant force is equal to the weight of the displaced fluid.
The story of Archimedes discovering buoyancy while sitting in his bathtub is described in Book 9 of De architectura by Vitruvius.

The weight of the displaced fluid is directly proportional to the volume of the displaced fluid (specifically if the surrounding fluid is of uniform density). Thus, among objects with equal masses, the one with greater volume has greater buoyancy.

Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water of weight 3 newtons. The force it then exerts on the string from which it hangs will be 10 newtons minus the 3 newtons of buoyant force: 10 − 3 = 7 newtons.

If the weight of an object is less than the weight of the fluid the object would displace if it was fully submerged, then the object has an average density less than the fluid and has a buoyancy greater than its weight. If the fluid has a surface, such as water in a lake or the sea, the object will floats at a level so it displaces the same weight of fluid as the weight of the object. If the object is immersed in the fluid, such as a submerged submarine or a balloon in the air, it will tend to rise.

If the object has exactly the same density as the liquid, then it's buoyancy equals its weight. It will tend neither to sink nor float.

An object with a higher average density than the fluid has less buoyancy than weight and it will sink.

A ship floats because although it is made of steel which is more dense than water, it encloses a volume of air and the resulting shape has an average density less than water.

Answer 2

In physics, buoyancy is an upward force on an object immersed in a fluid (i.e., a liquid or a gas), enabling it to float or at least to appear lighter. Buoyancy is important for many vehicles such as boats, ships, balloons, and airships

It was the ancient Greek, Archimedes of Syracuse, who first discovered the law of buoyancy, sometimes called Archimedes's principle:

The buoyant force is equal to the weight of the displaced fluid.
If the weight of an object is less than the weight of the fluid the object would displace if it was fully submerged, then the object has an average density less than the fluid and has a buoyancy greater than its weight. If the fluid has a surface, such as water in a lake or the sea, the object will floats at a level so it displaces the same weight of fluid as the weight of the object.

Answer 3

A boat floats, because the fluid in which it is floating offsets the downward pull of gravity and pushes it up.

The scientific name for this force, which allows even immense objects to float in liquid, is buoyant force, more commonly known as buoyancy.

A solid object's density determines whether or not the buoyant force of a liquid can lift it.

The density of an object depends upon its weight and its size. Given two solid objects that are different sizes, but weigh the same, the smaller, more compact object is the denser of the two.

Fluids also have density. When an object is placed in the fluid, it pushes aside some of the liquid and, if its density is greater than that of the fluid it displaces, it will sink and, if not, it will float.

Despite the enormous size of some ships, they are basically metal shells filled with air, and are less dense and lighter than the water they push aside, which allows the boats to float.

Answer 4

Ships float so long as they maintain the ability to displace more air below the water line than the amount of weight they place into the water.

Answer 5

Its not density, since ships are made out of steel, which density is heavier than water. But its because of the Pythagoras theorem : Any body sumerged in a liquid experiments an upward vertical force equal to the amout of liquid displaced by the same body. Whic means , the ship is hollow and it displaces enough water to create enough water preasure agains the bottom and side of the ship to keep it afloat. :), very simple. that s why when a ship takes water , it ll eventually go down to the bottom.

Answer 6

A boat will float equal to the amount of water it displaces.

Answer 7

remember Archimedes' principle..
The weight of the volume of water displaced by the ship is less than the weight of the ship.The ship is built in such a shape that the weight of the volume of the water displaced by it is more than that of the ship.hence it floats.

Answer 8

the air space in the ship make it float as air has a lower density than water

Answer 9

ships secretly believe in the FSM: faith makes them float. ;)

sorry. there were already too many good answers here, so I've nothing to offer but a lame joke.

Answer 10

water makes them float