gravity

Hanging a Hammer

This experiment involves balancing a hammer, a ruler, and some string. It is one of those balancing tricks that seem as though they just should not work, even though you understand the science behind them. I first learned it when I was eight years old, but it is still one of my favorites.

More Fish in a Bucket

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.

Fish in a Bucket

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.

Floating Bubbles

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.

919

Bowl of water on scale
I weighed this bowl of water. If I stick my hand in the water, and weigh it again, will it weigh more? If so, how much more. If not, why not?

945

plastic bag on scale
I weighed this plastic, storage bag while it was empty. Then I opened it to fill it with air. Sealing the bag again, I put it back on the scale. Was its weight the same, more, or less? Why?

946

Balloon on scales
A plastic, storage bag would not weigh more when it when it was filled with air, but when I blew up this balloon, its weight did increase. Why?

957

coiled snow structure
I photographed this snow structure on the drive home from the Utah Science Teachers Association conference. It is about six inches across, and there were many more of different sizes. How did it form?

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