What makes boats float?

Answer 1

Buoyance!:d
because of the design of the boat.

The overall density of the steel boat and air is less than the density of water.
A boat floats because it displaces the same mass of water as itself.

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.
A boat floats because its mass is less than that of the water it displaces; to put it another way, the total density of the boat is less than that of the water.

For example, consider an example made of aluminum. Aluminium has a density of about 2.7 grams per centimetre cubed - a lot more than water, at 1 gram per cc. if we squash that aluminum into a ball (or cube, or really any solid shape) it has that density and definitely won't float.

However, if we take our aluminum and shape a boat out of it, air now fills in the hollow. Air is so much lighter than water, and it floats quite easily. If we add up the mass of our air and our aluminum together, then figure out the density of the boat, it will be less than before (down to about half a gram per cc). Since this is less than the density of water, it floats.
Anything floats that displaces its own mass in water.

Objects that are less dense than water will float with some of the object above the water line eg cork, ice. Oil or fat floats as it is less dense than water. Humans float due to their fat content and possibly due to the air in their lungs.

Boats and ships have a shape that allows a large amount of air to become part of their overall structure. Like a basin sitting in a sink of water, the ship will float. This is due to it displacing a large volume of water now that it has air as part of its structure. However, the overall mass of the ship itself is greater than the overall mass of the same volume of water. If the ship tilts to take in water ie the air is displaced by water, then it will sink.
An object will float if it has less density than the water. In the case of ships, that includes any air trapped inside the ship.
Although a ship is heavy, it contains a lot of air, and its effective density is less than that of water. Another way of looking at this is, when you put a ship in water it displaces a lot of water (meaning, it pushes the water out of its way) and the weight of that displaced water is great enough to balance the weight of the ship.
Well two main reasons, the oxygen trapped in the ship is lighter than the water, so it counterbalances the weight of the ship.

Also the weight of water below the ship is greater or = to the ship.
A cruise ship (as any other floating object), displaces its own weight in fluid. This is call the Archimedes' Principle
Archimedes' principle, principle that states that a body immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. The principle applies to both floating and submerged bodies and to all fluids, i.e., liquids and gases. It explains not only the buoyancy of ships and other vessels in water but also the rise of a balloon in the air and the apparent loss of weight of objects underwater. In determining whether a given body will float in a given fluid, both weight and volume must be considered; that is, the relative density, or weight per unit of volume, of the body compared to the fluid determines the buoyant force. If the body is less dense than the fluid, it will float or, in the case of a balloon, it will rise. If the body is denser than the fluid, it will sink. Relative density also determines the proportion of a floating body that will be submerged in a fluid. If the body is two thirds as dense as the fluid, then two thirds of its volume will be submerged, displacing in the process a volume of fluid whose weight is equal to the entire weight of the body. In the case of a submerged body, the apparent weight of the body is equal to its weight in air less the weight of an equal volume of fluid. The fluid most often encountered in applications of Archimedes' principle is water, and the specific gravity of a substance is a convenient measure of its relative density compared to water. In calculating the buoyant force on a body, however, one must also take into account the shape and position of the body. A steel rowboat placed on end into the water will sink because the density of steel is much greater than that of water. However, in its normal, keel-down position, the effective volume of the boat includes all the air inside it, so that its average density is then less than that of water, and as a result it will float

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Any body is able to float in water when it is able to displace an amount of water which is equal to its own weight.So,if a ship is able to displace that amount of water it will certainly float.....
The ship displaces more than its weight of water. The difference between its weight and the weight of the sea water it displaces provides the buoyant force that pushes upwards against gravity.
Because the ship is hollow and filled with air the ship doesn´t sink but instead it floats.

Have you ever tried to put a ballon under water (when it´s filled with air) it doesn´t "want" to sink it "wants " to go up.

The ship sits partially below the surface of the water, and the amount of water it displaces weighs less than the ship, so the water pushes the ship upwards. This is called buoyancy.
Archimede's principle say if something/matter/a body displaces some amount of fluid equal or greater than the weight of the body,it will experience a upward force making it float. For better understanding dig a little in fluid mechanics/Buoyancy force.
Ships don't sink because air presses on the ship and keeps it buoyant.

A ship will float when the weight of the water it displaces equals the weight of the ship. This is the Achimedes Principle.

Water exerts a pressure on the hull of the ship with a net force pushing it upwards.

If the area of the hull is large enough, then at some point the weight of the ship will be balanced by the force pushing up on the ship.

This is why heavy solid objects sink, but keep making the surface area larger and it will eventually float.
Metal is denser than water. But if you consider the full volume of the ship (including the metal hull and the space inside it), on average the ship is less dense than water. Why does a helium balloon float into the air? The rubber of the balloon does not float into the air by itself. It's the same concept.
a boat can float because of the bouyancy
Actually, this is an easy question to answer.

The reason a boat weighing thousands of pounds can float on water is that the natural buoyancy of the water pushes up with exactly the same force as the boat's weight pushes down. The boat pushes away, or displaces an amount of water weighing the same as itself.

If the boat were heavier and pushed down more, the water's buoyancy would push up by the same increased amount.
Something floats if it displaces more weight in water than it weighs. That's why a big metal ship that weighs hundreds of tons can float: it displaces much more weight in water.

Answer

It depends on the density of a substance, if it can float or not. If its mass per volume is less than the one of water, it floats. That means overall that the same volume of water would have a bigger weight than the one of the ship... and it floats...

By the way: The volume of water the ship pushes away (under the water line) while floating, has just the weight of the ship. So if you're talking about a certain water deplacement of a ship, you're actually talking about the ship's weight.

An iron ship is no different from any other ship displacing as much water as they weigh. The use of ballast regulates the starboard and port sides of the ship if necessary and a ship with its cargo or without! The shape of the hull will also facilitate a larger or smaller surface area, incorporating the principles of boyancy!!!
Any object will float if it is less dense than water. Iron ships aren't solid iron; there are spaces with air in between.

The weight of the water that is displaced is greater than the weight of the ship, so it floats.
The simple answer is that ships, even those weighing hundreds of thousands of tons, weigh less than water. More-precisely, they weigh less than the amount of water they displace. To understand this better, let's do a mental experiment... Imagine a ship floating in water. Now imagine that the water turns into Jello and we remove the ship. That will leave us with a hole in the Jello of the exact size and shape of that part of the ship that was below the water. Finally, we fill the hole in the Jello with water. The weight of that water will be exactly equal to the weight of the entire ship. That's why the ship will float. This is because any floating body will displace an amount of liquid equal to its weight. As long as the weight of the displaced water is greater than the weight of the object, the object will float. If the weight of the water is less than the object, the object will sink. Here is another way to look at it, for a ship to float its mass has to be equal to the mass of the water it displaces OR equal to the density of the water multiplied by the volume of water it displaces. First imagine if the ship was shrunk down to a cube, but still had the same mass. when placed in water it will sink. why? because its volume isn't enough, when multiplied by the density of water, to equal the cubes mass. Now, if you had the same ship, same mass, but a giant shape to create volume, aka the hull, the ship will be able to float. This is, in short, how the size of the hull is chosen.
Cargo ships float because although they have a large volume, because of all the air inside the ship, they do not have a large density. For the ship to float it must be less dense than water. To find out the density of an object you must use this formula: Density= Mass divided by volume
Any object - ship or otherwise - will float if it has less density than the water (or other liquid on which it is supposed to float).

Think of the water that formally occupied the space below the surface now occupied by the ship. Clearly that doesn't sink! It is supported by the pressure of the water below. So all you need now is that the weight of the ship should equal the weight of the water it has displaced. If it weighs more than that, it will float a bit lower in the water until the balance is achieved. This is expressed by Archimedes' principle: Upthrust equals weight of water displaced. It also accounts for the curious way of quoting the weight of ships: "This ship has a displacement of 1000 tons" etc.
Because that's what they are designed to do. In physical terms, the density of the ship is less than the density of the water on which it floats.
It is because the inside of the steel ship contains a large volume of air, so its "overall density" is lower than the water displaced. The magnitude of the buoyant force always equals the weight of the fluid displaced by the object.

Example

Take an empty metal cup and place it in a sink full of water. It will almost always float, because of the buoyant force. Start adding water to the cup and it will start to sink. As the average weight of our ship (metal cup) increases, eventually it exceeds the weight of the displaced water and (like a sinking ship) it goes under.
how does ship float?

For Anything to Float, the density of the floating material must be less than density of the liquid.

Density = mass/volume

Density of water is ONE

and hence the ship is built in such a way that its mass is less than its volume and hence density is less than ONE hance the ship floats on water.

it is also to the fact that pressure is a factor of force/ area. so the greater the area lesser the pressure. similar is the concept why camel's feet does not sink in sand where as human's feet sinks.
Well, if you were to look at the plan of the titanic, its volume was mostly air, and air is has a density 1/1000th less than water, therefore it floats.
Because it is hollow in the inside, the air keeps it afloat. With so much air the ship is more bouyant then the water.

It depends on the density of a substance, if it can float or not. If its mass per volume is less than the one of water, it floats. That means overall that the same volume of water would have a bigger weight than the one of the ship... and it floats...

By the way: The volume of water the ship pushes away (under the water line) while floating, has just the weight of the ship. So if you're talking about a certain water deplacement of a ship, you're actually talking about the ship's weight ;-). Vic
A ship floats if it displaces its weight in water before it displaces its volume. If it were to displace its volume very much before it displaced its weight, it would sink quickly.

"Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object." Archimedes of Syracuse.

When a boat sits in the water, the water that was where the boat is now is moved. Because water always sits as low, then as wide as it can, when water has to move out the way, it has to move up.

Imagine if you have a tank of water and mark the water level on the side with a pen. Now float something in the tank. You will see that the water level is now higher than your original mark.

Now, this water that is higher is pushing down on the rest of the water, just like the boat is. The pushing down of the water that was moved out of the way always equals the amount that the boat is pushing down.

Another way to consider it is if you weighed the boat and it weighed 100kg. Then if you filled a tank up to the very top with water and put a hose on the overflow hole to collect the water in a bucket. Then you put the 100kg boat in the full tank and let it float. All of the water that the boat pushed out of the tank and overflowed into the bucket would weigh exactly 100kg.
The basic idea is called Archimedes' Principle. An item floats when it displaces more than its own weight of the liquid that it's immersed in. The surrounding fluid pushes back with a force equal to that of the amount displaced, so when the two are equal the object floats.

The lower the density (weight per unit of volume) of the object being immersed, the more readily it will float because it more easily displaces its own weight. So, even though a ship can weigh thousands of tonnes its hull encloses a lot of air, meaning its density is relatively low. If some giant were to come along and crumple the ship into a solid ball of metal, it would occupy much less space and thus wouldn't displace as much water, so it would sink quite quickly. Think Titanic, for example:

When the titanic hit the ice Berg the water got in which made the boat sink.
The overall density of the boat is less than that of water.
If the mass of the boat is less than the weight of the water it displaces then it will float.

Say hello to Archimedes principle.

most people believe that the bottom of the boat plays a big part, it does.. but not significantly. it's all physics, it has to do with displacement. the boat displaces a certain amount of water according to its mass. that counterforce that the water puts on the bottom of the boat keeps it afloat.