Archimedes Principle and Buoyancy

Archimedes was one of the leading scientists and mathematicians of antiquity. One of his famous discoveries involved a crown made for King Hiero II. The king asked Archimedes to find a way to figure out if his new crown was made of solid gold without destroying it. Legend has it that Archimedes had the first Eureka moment when he was taking a bath. He discovered that objects that sink displace their volume in water. He was so excited by his discovery that he ran down the streets naked shouting “Eureka” which means “I have found it” in Greek. By weighing the crown and measuring its volume Archimedes could determine if the crown was solid gold or a mixture of gold and other metal. 

There is some doubt, however, if this was the actual method that was used since the displacement would be hard to measure. Some think that Archimedes actually weighed it in and out of water to determine its density. This is depicted in the animation. You can see that the crown does not weigh as much as the gold block when it is immersed. You will learn about how this works in this topic.

What Causes Buoyant Force?

View this presentation to learn why buoyant force occurs and how to calculate it.  You will also learn how to use specific gravity to determine if objects will float or sink.

View a printable version of this interactivity.