Archimedes' Principle
by Pam Collinge
November 10, 2008
Sixth graders tested the buoyancy of an aluminum boat and a foil ball. Students found that when they dropped the ball of aluminum foil in the water, it had a completely different result than the boat. Although both pieces of aluminum foil have the same weight, the ball takes up a smaller space than the boat. The amount of water pushed aside by an object equals the force of water pushing upward on the object. The larger boat pushes more water out of the way than the ball and creates enough upward force to cause it to float.
Archimedes was the scientist who discovered this principle. The principle states “any body partially or fully submerged in a fluid is buoyed up by a force equal to the fluid displaced”. Archimedes is said to have made this discovery while in the bath. He was given the task of finding out if a goldsmith, who worked for the king, was carefully replacing the king's gold with silver. While doing this, Archimedes decided he should take a break and went to take a bath. While entering the bath, he noticed that when he placed his legs in, water spilled over the edge. Struck by a moment of realization, he shouted "eureka!" He ran to the king and told him that there was a way to positively tell if the goldsmith was cheating him. Archimedes knew that silver and gold have a different density, (gold being the heavier one). So he placed a crown made of gold and the king's crown into a pool, the two being of equal weight. (Archimedes' idea was that if the king’s crown overflowed more than the gold crown that meant the goldsmith was cheating the king. By this test they found that silver had been put into the king's crown and the goldsmith was executed.
Information obtained from Wikepedia.
