Last time I left you with a question. We were imagining fish swimming in a container of water. When I was a child, I was told that you could put the container on a scale, and as long as the fish did not touch the sides or bottom; you would only be weighing the water.
We substituted a brick for the fish, and found that if we lowered it into the water, the scale went up enough to equal the weight of the water it displaced. Then we placed it on the bottom, and found that the scale went up to equal the full weight of the brick.
This week's experiment goes back to fishing trips from my childhood. As we caught fish, we put them into a large tub of water. I loved watching them swim around and around. I was told that if you weighed the tub, that it would not register the weight of the fish, unless they touched the sides or bottom of the tub. Was that right? Let's find out.
This experiment is one of the classics that is still a lot of fun to play with. It has to do with density. Density can be a difficult concept to grasp, but it is much easier once you have played with a density column.
Imagine that I have three cups that are the same size. If I fill one cup with water, one with sand, and one with lead. Would they all weigh the same? No, of course not. A cup of sand weighs more than a cup of water. Sand is denser than water. Lead is denser than sand, so a cup of lead weighs more than a cup of sand.
This time we are going to produce some floating bubbles. Instead of filling the bubbles with hydrogen or helium, our bubbles will be filled with ordinary air, and will be floating on a layer of a heavier gas.