Do you love to play in the water? We sure do! Whether it's in the ocean, at a pool, or just in the bathtub at home, we can't get enough of playing in the water.
Have you ever noticed how you seem to weigh less when you're in the water? As you float and swim along, you notice that you can move in ways that just aren't possible when you're on land.
You may have also noticed that you seem a lot stronger when you're in the water. If you ever play with a buddy, you may have tried to lift each other into the air when you're on land. If you have strong muscles, you might be able to lift your friend for a bit, but he gets heavy after a while.
When you're in the water, though, lifting your friend isn't nearly as difficult. In fact, your friend probably seems to weigh a lot less. Why is it easier to lift a heavy object when you're in the water than on land?
The answer lies in the scientific concept of buoyancy, and you can thank Archimedes for the explanation. Archimedes was a Greek mathematician, engineer, inventor, and astronomer who lived over 2,000 years ago.
Legend has it that Archimedes discovered the scientific concept of buoyancy while he was taking a bath. As he stepped into the bath, he noticed that the water rose. The more of himself he put into the water, the more the water rose. Realizing what was happening, Archimedes allegedly jumped out of the tub and ran naked into the streets, shouting “Eureka!" (which loosely translates from Greek to English as “I found it!").
No one knows for sure whether Archimedes really went streaking after making his discovery. What we do know, though, is that his discovery was a scientific breakthrough that is often referred to today as Archimedes' Principle.
What Archimedes discovered was the scientific principle of buoyancy, which holds that an object submerged in water displaces water according to how much it weighs. In fact, the water will push upward against the object with a force equal to the weight of the water it displaces.
How much water an object will displace will depend upon its density, which is a measure of how much mass is in the object relative to its volume. For example, a bowling ball and a beach ball that are the same size will have the same volume. The bowling ball, however, is more massive and thus denser than the beach ball.
Can you guess what will happen if you drop both the bowling ball and the beach ball in the water? The bowling ball will sink, and the beach ball will float! But why?
In both cases, the water pushes up against the ball with a force equal to the weight of water it displaced. In the case of the bowling ball, it weighs more than the amount of water it displaced, so it sinks. The beach ball, however, displaces very little water and the air inside it is much lighter than the weight of the water it displaced, so it floats!
In fact, we bet that you've experienced the force of buoyancy for yourself at one time or another. Have you ever played with a beach ball in the water? If so, you've probably tried to push it underneath the water. The resistance you feel when you try to push a beach ball under water is the force of buoyancy at work!
It's that same force of buoyancy that makes you seem super strong when you're in the water. That friend of yours who is so heavy on the land seems a lot lighter in the water because of buoyancy. It's easier to lift your friend in the water, because the water itself pushes against your friend, helping you lift him much easier than you could ever do on land!