Buoyancy

[Catapult]

Hello,

 

I want to know more about buoyancy.

 

How ship floats? We know that ship is much denser than water. Somebody had told me that it floats because it is open and therefore there are air on it and air is less denser than water.

 

However, I don't know the formula on how to get the overall density if the air already involves. Would somebody give me the formula on how to get the overall density wherein air involves, like the overall density of ship?

 

One more,

If the object has exactly the same density as the fluid, then its buoyancy equals its weight. It will remain submerged in the fluid, but it will neither sink nor float, although a disturbance in either direction will cause it to drift away from its position.

 

So what does the above quoted statement means? Meaning the submerged object is in the center of the fluid?

 

Any help will be greatly appreciated.

 

Thank you.

Edited November 7, 2011 by Catapult

[J.C.MacSwell]

Hello,

 

I want to know more about buoyancy.

 

How ship floats? We know that ship is much denser than water. Somebody had told me that it floats because it is open and therefore there are air on it and air is less denser than water.

 

However, I don't know the formula on how to get the overall density if the air already involves. Would somebody give me the formula on how to get the overall density wherein air involves, like the overall density of ship?

 

One more,

 

So what does the above quoted statement means? Meaning the submerged object is in the center of the fluid?

 

Any help will be greatly appreciated.

 

Thank you.

 

The simplest formula generally is that the buoyant force is equal to the displacement (weight of volume of water displaced)

 

It means it could be anywhere in the fluid. Unless a change in pressure changes the density of the object it will tend to stay where it is, or continue on it's path. It has neutral buoyancy.

[michel123456]

http://en.wikipedia.org/wiki/Archimedes'_principle

[Mellinia]

Hello,

 

I want to know more about buoyancy.

 

How ship floats? We know that ship is much denser than water. Somebody had told me that it floats because it is open and therefore there are air on it and air is less denser than water.

 

However, I don't know the formula on how to get the overall density if the air already involves. Would somebody give me the formula on how to get the overall density wherein air involves, like the overall density of ship?

 

Basically they make the ship to occupy as much volume as possible, while still the same mass. The density of both air and ship can be calculated by the density equation, just get their total mass and total volume. According to density equation: density= mass/volume. Density is inversely proportional to the volume. The total mass of the ship and the air is approximately near the mass of the ship, but the volume that a ship-sized piece of metal occupies (because it is hollow) is more than a same piece of metal that is not hollow. Thus, the overall density is decreased....Anyone has got numbers?

[swansont]

So what does the above quoted statement means? Meaning the submerged object is in the center of the fluid?

 

No force means it will stay at rest if placed at rest. So wherever you put it, it stays.

[Catapult]

Basically they make the ship to occupy as much volume as possible, while still the same mass. The density of both air and ship can be calculated by the density equation, just get their total mass and total volume. According to density equation: density= mass/volume. Density is inversely proportional to the volume. The total mass of the ship and the air is approximately near the mass of the ship, but the volume that a ship-sized piece of metal occupies (because it is hollow) is more than a same piece of metal that is not hollow. Thus, the overall density is decreased....Anyone has got numbers?

Hello,

 

Thank you for your answer.

 

I read somewhere that the total density of ship is lower than water. So is that what you mean?

 

No force means it will stay at rest if placed at rest. So wherever you put it, it stays.

 

Thank you for your answer.

 

But for example, I submerge some object which has the same dense as water in a water. What is the position of that submerged object?

 

Or it is like that, if I push upward the submerged object, then it will float and if I push it downward, it will sink?

 

Thank you michael123456 and J.C.MacSwell as well for your replies.

 

Any help will be appreciated.

[michel123456]

The position will be anywhere in the liquid. The lightest force will make the object change position and direction. If you push it down it will go down, if you push it up it will go up. But it will not float like a boat. Once you push the object above the surface, the part out of the water will start to weigh and push the object down.

 

This 2 tons hippopotamus has about the same density with water.

Edited November 8, 2011 by michel123456

[swansont]

But for example, I submerge some object which has the same dense as water in a water. What is the position of that submerged object?

 

Wherever your hand was when you released it.

 

Or it is like that, if I push upward the submerged object, then it will float and if I push it downward, it will sink?

 

There's quite a lot of friction involved, so the object will stop moving eventually if there is no net force.

[Catapult]

Thank you very much swansont and to others who have replied.

 

I have one more question about your statement.

 

Wherever your hand was when you released it.

For example my hand was in the center of the water when I submerge the object so meaning the submerged object will be in the center as well until some force change its position?

 

Thank you very much.

 

Any help will be appreciated.

Edited November 9, 2011 by Catapult

[swansont]

I have one more question about your statement.

 

 

For example my hand was in the center of the water when I submerge the object so meaning the submerged object will be in the center as well until some force change its position?

 

If it was at the center and you released the object at rest, it will remain at rest since there is no net force acting on it — that's from Newton's first law. A new force will move it.