Harvey Berkal, age 12, of Winnipeg, Manitoba, Canada, for his question:
What is the principle of Archimedes?
This law of physics never fails its tests and nobody disputes it. It states the ratio of buoyancy and since it is a basic law it is widely useful as a guide and a measuring unit. For example, the principle of Archimedes is used to gauge the buoyancy of a boat and the density of a new plastic.
The great thinkers of ancient Greece were highly respected by the citizens and nobles of their day. In the second century B.C., Archimedes enjoyed life in the Sicilian city of Syracuse. But even his devoted neighbors never dared to suspect that the Twentieth Century would rate their home town genius among the greatest brains of all human history.
Archimedes was basically a mathematician. The problems that fascinated him most were about different substances, their weights and volumes and the forces that made them move. This field of matter and energy is the vast and practical science we call physics. And Archimedes was a practical man. He is called the Father of Experimental Science because he tested his ideas. What's more, he used his basic discoveries to create such practical inventions as the pulley and the lever.
'The principle that bears his name began, of all things, with a crime detecting problem. The King of Syracuse asked him to prove whether a royal crown was made of gold, as it should be, or of a mixture of gold and silver. Archimedes knew that a brick of pure gold is heavier than an equal sized brick of silver, or of gold and silver alloy. He could compare the weights and volumes of two bricks. But the volume of a fancy shaped crown was a tougher problem. Archimedes solved it and the criminal case in his tub.
He figured that the water he displaced in the bath was equal to the size or volume of . his body. So he could find the volume of the crown by dunking, it and measuring the amount of the water it displaced. He then dunked a bar of pure gold, equal in weight to the crowd, and noted that it displaced less water. The crown's material, therefore, was an alloy lighter than pure gold and the King's goldsmith was proved a fraud. We use this basic method to determine the density or specific gravity of solids, liquids and gases. This is not the famous principle of Archimedes, but it led to it.
The solution of volume led Archimedes to ponder deeper problems about the buoyancy of objects in fluids. He already knew that the volume of a submerged object exactly equals the volume of the water is displaces. But floating objects appear to lose some of their weight. Archimedes figured that the weight apparently lost by a floating ship exactly equals the weight of the water it displaces. This is the famous principle of Archimedes. The basic law never fails. It still governs the buoyancy of a ship. A submerged boulder is still lighter by the same weight of water displaced by its size.
The branch of modern science that deals with fluids is hydrostatics.Its basic laws must be known and used by ship designers and irrigation planners and they never neglect or dispute the famous principle of Archimedes. And lab researcher still use the famous old dunking trick that led to the buoyancy principle. They use the same methods with much refined instruments to find the density of a submerged object by comparing its volume with an equal volume of water.