How do ships stay afloat??
Answers:
It is just magic !
The "displacement" theory is just a con.
When the bottle of champagne is smashed against the side of the boat, all the little "magic" bubbles then help keep the boat afloat.
Because they displace more water than they weigh. ie; if a ship weighing 10,000 tonnes displaces the equivalent of 20,000 tonnes of water, then it will float.
The buoyancy of the air inside the vessel creates more uplift than the weight of the vessel itself does downwards.
Air is less dense than water.
Lots of tiny fish swim along under the boat holding it up in the water.
Water is made up of molecules in motion. This creates a resistance to objects entering it. If there is any buoyancy to the object, this combines with the resistance to keep it afloat. Now for something as large as a ship, it requires a large amount of water. The same vessel would not float in shallow water.
Simple answer:
Compare a balloon filled with air and the same balloon filled with water. You know that a balloon with air can be the same size as the balloon with water, but the one with air floats on water. The ships are not filled with machines and metal only, they have air inside of them, and things that are lighter than water, such that they are like big balloons that are not totally filled with water.
If you put the 2 balloons on a see-saw, the one with water will go down not the one with air, even though they have the same size. Now imagine the ship that is totally water and no space in it, compared to a ship that is like a metal balloon full of air, the ship that is totally water will go down but the metal balloon of air goes up if they are on the see-saw.
Now if you want the see-saw to be balanced, that is, horizontal, you need to start taking away some water from the water balloon. Before you take away all the water, the see-saw is balanced already. The water remaining on the see-saw is the same weight as the metal balloon, but you realise that it is a smaller size. So now you know that as long as the metal balloon can take up that same, smaller sized space in the water, it can be balanced by that same, smaller sized amount of water.
Scientific answer:
By displacing the volume of water that has the equal weight as their own weight. In other words, if the ship has a weight of 1 ton, and it is able to displace 1 ton of water without its entire volume being submerged, it floats.
In other words, ship has enough volume to displace a volume of water that has the same weight as the ship. There will be remaining volume for the ship, such that if you try to push the ship down, the ship will displace more water of the same weight until the weight balances the magnitude of the force you are applying, and the ship will not sink further.
NOTE: It does NOT displace water of MORE weight than it's own.
By two principles: Archimede's Principle states that the upthrust on a submerged body is equal to the weight of the displace fluid.
Note that it is equal not more or less than.
Principle of flotation states that when an object floats, the upthrust acting on it must be equal to its own weight.
What is upthrust? When you submerge an object in a fluid, the object will experience a difference in pressure between its lower and upper surfaces, this difference in pressure results in an upward force called upthrust.
Think about placing a ball that floats in water. Let us imagine that half the ball goes underwater and half remains on top. The half that has gone underwater, has to be able to "push" away that same amount of water that the half of the ball takes up in space. If you imagine the ball to be in a cup, you would know that the water level would rise, because the ball has "pushed" away some water and this "push" is holding up that amount of water above the original level. The weight of this amount of water would be equals to the weight of the "push". So in other words, the weight of the ball is equal to the weight of the amount of water "pushed" away.
Imagine a U shaped tube with water in it, and a "plunger" in one end of the tube. The water level in both ends are the same at the start, but when you put a object of weight "N" on the plunger and the plunger moves down, it will continue to move down until the water level on the other end of the U tube rises up by the same distance it moved down in it's own "tunnel". So you can see that the water moved up in the other tube has the same weight as the object in the tube with the plunger. Like a balance.
Sir:
Ships stay afloat by displacing water, i.e., moving it out of the way. Water has weight. A ship has weight. A ship displaces its own loaded weight of water when it is in the water. Think about it. You never see the bottom of a ship when it is in the water, only the upper part.
A ship begins to sink when it cannot displace more water than the weight of the ship. For example, if a leak in the hull occurred, and water began to come into the ship, the ship's total weight would increase. The speed of water coming into the ship would determine how fast the ship starts going down until there is nothing left above the water.
an easy test .
get something that floats that will fit in your bucket or tub
Fill the tub to the top
slowly put the thing that floats in the water
All the water that spills over the side basically weighs the same as the floating thing
take the floating thing out, and you'll see the water has gone down in the tub. That amount of water was "displaced".
EXPLAINATION:
the ship builder knows the ship is heavier than the water, so makes it long and wide enough so the amount of water "displaced" (see above) eg. 5 tons, is the weight of the ship. Now the builder knows some of the ship will be below water level. He just has to make the sides high enough while allowing for "displacement" to make sure the ship will not take on water.
Have a look in the harbour and the ships that carry the heavy stuff ars long and wide. Those ship builders are pretty smart
Today, ships are made of steel and lots of heavy stuff. Some can weigh around 80, 000 tons. How can any of them possibly stay afloat? The reason is simple, and you can make your own ship float too.
All you need is:
aluminum foil,
a few paper clips,
an empty aquarium (or similar large container)
and water
Here's what you do:
Partially fill the aquarium or container with water.
Take the aluminum foil, bend it in half and make a boat. Does it float?
Add a few of the paper clips. Now, what happens?
Take another sheet of aluminum and tightly fold it in half, placing the same number of paper clips as in the first boat inside the flattened one. What happens?
Here's how it works:
The aluminum in the boat shape displaces more water than the flattened one. If the object has enough volume to displace an amount of water equal to its own weight, it will float. Its weight, or the force of gravity, will equal its buoyancy, or the force of the water pushing up on it.
Does a cup of saltwater weigh more than a cup of fresh water? Let's find out!
All you need is:
measuring cup
Jar
Water
Scale
Salt
Here's what you do:
Fill the measuring cup with one cup of water and use the scale to measure how much it weighs. Write it down.
In the jar, pour a little more than a cup of water. Stir in as much salt as the water will hold.
Pour one cup of the saltwater into the measuring cup and weigh it. Write it down. Does the saltwater or freshwater weigh more?
What's the result?
Though there were equal volumes of the saltwater and the freshwater (one cup each), the saltwater weighed more. This means it is heavier and thus more dense than the freshwater.
What do you think? Is saltwater denser than fresh water?
All you need is:
1/4 cup salt
2 cups water
2 clear 16 oz. glasses
eye dropper
food coloring
2 eggs
Here's what you do:
Fill glass with 1 cup of water.
Drop egg in glass. What happens?
Fill a second glass with 1 cup of water. Add salt and stir until dissolved.
Add a few drops of food coloring. Let sit for 5 minutes.
Add more water carefully by trickling it along the side of the glass so as not to disturb the settled colored saltwater. You may wish to use the eye dropper to add the water gently.
Drop egg in glass. What happens?
Compare how the eggs float in the two glasses. What's the difference? Why?
Here's how it works:
The reason the egg acts differently in saltwater is because of density (the weight of the liquid divided by the amount of space it occupies). The egg has a greater density than freshwater, so it sinks. When salt is added to the water, its density becomes greater than that of the egg. This means that the egg will begin to float.
or you can chech this answer also :
An object which sinks completely displaces an amount equal to its volume; Archimedes' Principle states that when this happens, the weight of the object is reduced by its volume times the density of the fluid. If the weight of the object is less than this quantity, it will float; the amount of fluid displaced is directly related (via Archimedes' Principle) to its weight.
Displacement is often used as a measure of the size of ships. The displacement of a vessel is defined as the weight of the amount of water it displaces when afloat. The size of a naval ship typically is reported as the number of long tons of water she displaces, but the measure is less often used for passenger ships or cargo ships. See tonnage.
Also, a displacement hull pushes its way through water, being supported entirely by displacement, as opposed to a hydroplaning hull, which glides over the surface of the water while being partially supported by hydrodynamic forces caused by the motion of the hull across the water, or a hydrofoil, which lifts the hull from the water entirely, using underwater wings.
they don't! It's an optical illusion! What happens is that there is a bloke with a top hat and a cape in the boat who makes it appear to float, when really it's still in Bristol or Portsmouth or somewhere! Every time you think you've been on a boat you were hipnotised! you have never been abroad.
The same is true for areoplanes!
its all physics
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