I found a fun experiment at spartechsoftware.com that involves the kitchen sink. The web site asks this question “How does a boat or ship carrying hundreds of pounds worth of stuff float while that same stuff would sink to the bottom of the ocean if dumped overboard? How come when you’re in a pool and you stretch your body out flat you float. But, if you wrap your arms around your legs and curl up into a ball you sink? Well, it all has to do with how much water is pushing against you and a little scientific principle called buoyancy or flotation.”
To test this, fill your sink with water. Then get some clay. Split the clay in two different pieces. Make one piece into a ball, then make the other into a boat shape. Place these into the water to see what happens.
What has happened is explained as “if the total area of the object that makes contact with the water is large enough, the object floats. The object must make room for its own volume by pushing aside, or displacing, an equivalent (or equal) volume of liquid. The object is exerting a downward force on the water and the water is therefore exerting an upward force on the object. Of course the floating object’s weight comes into play also. The solid body floats when it has displaced just enough water to equal its own original weight.”
I will definitely try this one with my kids, it doesn’t sound like it would make too big of a mess.
Would you try this one?