I. The Principle of Buoyancy

Buoyancy is the ability of bodies to float. Buoyancy is the resultant vertical force exerted on an object by the object in which it is in or floating in. That means that if something is lighter than the substance it is in, that object will be pushed up. Buoyancy in objects can change when something is added to the substance that they are floating in.

The strength of the buoyancy, or the amount of force pushing the object up, is equal to the weight of the fluid displaced. That theory, formulated by Archimedes, who lived in Greece about 2,250 years ago, supposedly was discovered in this way: Archimedes was just relaxing when he was summoned by the king. The king had a problem for Archimedes, namely that the king had just received a new crown. The smith who made the crown claimed that the crown was made out of pure gold. The king, though, had his doubts. He said that if in fact the crown was not made of pure gold, the goldsmith would be executed. The king had no idea how to tell whether the crown was in pure or not. It was up to Archimedes to solve the problem.

Archimedes decided to take a bath while he pondered over the problem. The bathtub was filled to the very top, and he jumped in. The unavoidable happened, of course, and some water spilled out. As soon as Archimedes saw this, he jumped out of the bathtub and started running around town yelling "Eureka!" What had he discovered? Simply that when he got in the water, The weight of the water that spilled out of the tub, or displaced, was equal to his buoyancy. If that were also true for other objects,then the king could easily figure out whether the crown was pure or not by comparing the amount of water displaced by the crown and by a lump of pure gold. The method was tested, and, as it turned out, the crown was not pure and the smith was killed.

Even though many people don't realize it, buoyancy is a very important part of our daily lives. Buoyancy makes many things possible in our lives, like boats, navigational instruments like buoys and some tools. Some boats, like the hydrofoil, use buoyancy so efficiently that they seem to "fly" over water.

The level, a very important carpentry instrument for checking whether things are level or not, uses buoyancy. The level is basically a stick with three tubes of water attached to it. One tube is side-to-side, the other is diagonal, and the third is forward and back. Each of the tubes has a small bubble of air in it. When the level is not perfectly flat, one end of at least one of the tubes on the level is higher than the other. Since the bubbles are lighter than water, they float to the top. There is a marking right by each of the tubes to show where the middle is.

Another use for buoyancy is in buoys. Buoys float out at sea to show ships how deep the water how far away from land the ships are, and many other things. Buoys have a special "language" of flashes and patterns that captains have to understand. Another very important use for buoyancy is in balloons. Although it is not obvious, buoyancy is what makes balloons float. Blimps, zeppelins, hot air balloons, and party balloons all wouldn't float without buoyancy. Buoyancy keeps different parts of the atmosphere separate, and keeps precious oxygen from sinking into the sea (silly idea, isn't it?).

All in all, a world without buoyancy would beunimaginable and impossible. Buoyancy is a very important part of our lives and it would be impossible to live without it.

II. A Buoyancy Experiment:

 

A Raft Made of Bottles

Start by collecting these materials:

6 2 ltr. bottles

A nylon string

6-pack holders

Scissors

Next, then take the labels and the rings around the tops off the bottles and rinse the bottles out.

Then tie the 6-pack holders together with the string.

Then tie the bottles into 2 groups of three each using the 6-pack holders.

Then tie two groups together to make a total of 1 group of six bottles.

NOW YOU ARE READY TO FLOAT ON WATER!!!!!!!!!