What was Archimedes' contribution in Physics?

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2012-11-14 17:12:58

There were many. He is famous for the saying, "If I had a lever

big enough I could move the world." Actually, a more accurate

translation would be: If I had a firm enough place to stand, I

could move the world.

He is also most known for hi invention of the Archimedes screw

for pumping water.

"Archimedes'_principle" id="Archimedes'_principle">Archimedes'


Main article: Archimedes' principle

Archimedes may have used his principle of buoyancy to determine

whether the golden crown was less dense than solid gold.

The most widely known anecdote about Archimedes tells of how he

invented a method for determining the volume of an object with an

irregular shape. According to Vitruvius, a votive crown for a

temple had been made for King Hiero II, who had supplied the pure

gold to be used, and Archimedes was asked to determine whether some

silver had been substituted by the dishonest goldsmith.[15]

Archimedes had to solve the problem without damaging the crown, so

he could not melt it down into a regularly shaped body in order to

calculate its density. While taking a bath, he noticed that the

level of the water in the tub rose as he got in, and realized that

this effect could be used to determine the volume of the crown. For

practical purposes water is incompressible,[16] so the submerged

crown would displace an amount of water equal to its own volume. By

dividing the mass of the crown by the volume of water displaced,

the density of the crown could be obtained. This density would be

lower than that of gold if cheaper and less dense metals had been

added. Archimedes then took to the streets naked, so excited by his

discovery that he had forgotten to dress, crying "Eureka!" (Greek:

"εὕρηκα!," meaning "I have found it!"). The test was conducted

successfully, proving that silver had indeed been mixed in.[17]

The story of the golden crown does not appear in the known works

of Archimedes. Moreover, the practicality of the method it

describes has been called into question, due to the extreme

accuracy with which one would have to measure the water

displacement.[18] Archimedes may have instead sought a solution

that applied the principle known in hydrostatics as Archimedes'

principle, which he describes in his treatise On Floating

Bodies. This principle states that a body immersed in a fluid

experiences a buoyant force equal to the weight of the fluid it

displaces.[19] Using this principle, it would have been possible to

compare the density of the golden crown to that of solid gold by

balancing the crown on a scale with a gold reference sample, then

immersing the apparatus in water. The difference in density between

the two samples would cause the scale to tip accordingly. Galileo

considered it "probable that this method is the same that

Archimedes followed, since, besides being very accurate, it is

based on demonstrations found by Archimedes himself."[20]

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