how dose an object floats on water?

Question

as we can see ships and boats on sea and also objects floats on water

Answer 1

the air in them like a flotation thing the air keeps it up and your body if your laying down

Answer 2

1) Water exerts pressure on anything that is inserted in the water, whether it is completely submerged or (as with a boat) only partly submerged.

2) This water pressure pushes on the object on all sides. Think of the pressure as a bunch of tiny arrows hitting every part of the object that is submerged. The "pressure arrows" on the object's left side point to the right; the "pressure arrows" on the right side point to the left, the "pressure arrows" on the object's bottom point upward, etc.

3) All the "left" and "right" pointing pressure arrows cancel each other out (because they're opposing each other). So what you're finally left with is an upward-pointing pressure. This is called "buoyancy."

4) It turns out that the total amount of buoyant (upward-pointing) force, depends upon how great a volume of water is "displaced" (that is, how much volume is moved out of the way to make room for the object). The greater the amount of displaced water, the greater the buoyant force.

5) If the upward force of buoyancy exactly matches the force of gravity pulling down on the boat (i.e. its weight), then the boat will neither move up nor down. That is, it will float.

So, the way to make a boat float is to increase its volume a lot (so that it will displace a lot of water and will have a lot of buoyant force pushing up); but don't increase its weight very much. This is the same as saying: decrease its weight-to-volume ratio, otherwise known as its density.

If you take a floating boat and push down on it a little, it displaces more water. This cause the buoyant force to increase so it exceeds the boat's weight, and the boat will bob back up when you let go of it. Likewise, if you pull it up a little out of the water, the boat displaces less water, so the buoyant force decreases, and the boat's weight causes it to fall back down.

Answer 3

Archimedes discovered the principle of displacement while he sat in his bath and famously leapt out shouting "Eureka!" (I have found it!).

As a body is immersed in water, the force of the body acting downwards due to gravity is met by the force of the water pushing back up. And the force of the water pushing back up is determined by the force of air pressure pushing down on the water in the first place.

Depending on the _relative_ density of the water to the object immersed in it, the object will either float on top (if it's density is less than that of water) or it will float within (if it's density is equal to that of water - called neutral buoyancy) or it will sink (if it's denisty is greater than that of water).

The weight of the object is not the important factor - it is the _relative density_ that is the deciding factor.

If you take a cork that weighs a few grams, it will float.

Take a piece of steel and it will sink.

But f you take a piece of steel and shape it into a boat with a large expanse of air on the inside, the overall density of this vessel is less than that of the surrounding water and the vessel will float.

Answer 4

Yes. Buoyancy is displacing the object weight in water. Since salt water is more dense than fresh water, a ship weighing 100 tons will have a lesser draft in salt water. Fresh water weighs about 62lb per cubic foot and saltwater weighs about 65lbs for the same volume.

Answer 5

The buoyant (upward) force on an object equals the weight of the fluid it has displaced. So, if you have a ball with a volume of 2 cubic feet, and it is floating half-submerged, it is displacing 1 cubic foot of water. 1 cubic foot of water weighs about 62 pounds, so the water is exerting a buoyant force of 62 pounds on the ball.

Since the ball is neither rising nor falling, it must weigh 62 pounds. The force of gravity (its weight) balances the buoyant force of the water.

Answer 6

Bodies floats on the water because they are lifted or carried by a force equal to the weight of the water which it press aside.
This is the law of Boile-Mariotte written in not very good English.

Answer 7

It is very simple.

Ships and boats can float because they are cup shaped.

Therefore when it sinks down to the water, there are still air inside the ship, so it floats! If water goes inside the ship, and air goes out, it sinks.

If you see in movies, when ships gets hit by cannonball and water goes into the ship, it drowns. Because there is not enough air within the ship to float.

Answer 8

This has to do with density, which is mass divided by volume. Some objects start out with a density of less than water (1 gram per cubic centimeter), so they float naturally (like wood, oil, etc.). With things like steel boats and so forth we have to cheat. The construction design needs to make the overall volume of the boat big enough so that the craft's resulting effective density is less than that of water. This works real well, and there are lots of boats made of high density materials which float, even though the stuff they are constructed from doesn't.

As the story goes, Archimedes was bathing in a public bathhouse several thousand years ago when he noticed the water level rise around him in the tub. Truly thrilled by his apparently miraculous realization, he jumped out of the tub and ran through the streets naked screaming "Eureka!!! Eureka!!!" (I've found it!!! I've found it). What Archimedes had discovered is now referred to as Fluid Displacement. He had noticed that when a body is submerged in a fluid, that body displaces a volume of the fluid equal to its own. That is, to say, that if I placed a cubic meter block of stainless steel into a pool (don't ask me how), the block would displace exactly one cubic meter of water. Simple, right?

Anyway, back to our naked friend. Archimedes also noticed that the objects felt lighter when they were submerged. This phenomena made him want to quantify this observation. After a while, Archimedes made the wonderful discovery that the objects were buoyed up by a force equal to the weight of the fluid that they displace.

So let's take a look at our block in the pool. That cube of stainless steel (which is more dense than water) would have a mass of approximately 8020 kg or would weigh 78596 N. As we learned before, the cube would displace one cubic meter of water, which has a mass of (quite conveniently) 1000 kg or a weight of 9800 N. So the cube would be pushed up, in effect, by 9800 N of water. 78596 (its real weight) - 9800 (what's pushing up on it) = 68796 N (its weight while submerged). Great, now you know this thing weighs 9800 N less while I try to get it out of my pool.

Now let's try something we know is less dense than water. We'll take, oh I dunno, cedar wood, which has a density of .49 g/cu cm. Keep in mind that water's density is 1 g/cu cm. So if I had one cubic meter of wood (if you haven't noticed by now,I go to Price Club), which has have a mass of 490 kg, it would, if forced underwater, displace, again, one cubic meter of water. This displaced water has a mass that is greater than the object being submerged, so in other words, the water is pushing up harder than the wood is pushing down. The wood will float at a position such that the submerged portion would displace a volume of water whose mass is equal to the mass of the entire block. Or the wood would displace its weight in water.

Humans are only slightly less dense than water, which is why we must submerge a large portion of our bodies to stay afloat (more displaced fluid means greater force pushing upwards). Women are less dense than men (due to a higher fat percentage), which is why it is easier for women to float than men. It's not our fault, it's science!


Now try to use what you just learned to figure out how a boat made out of stainless steel can float!

Answer 9

Things float because they weigh less than the their own volume of water.

Answer 10

Because they are pushed up by the force equivalent to the weight of the water they displace known as Archimedes Principle. That is why ships are measured by displacement tonnage.

Answer 11

something will float if it:


weighs less than the volume of water it displaces