force and interactions


Ball on paper plate
If I roll the ball around the paper plate in the direction of the blue arrow, when it gets to the place where I cut out part of the plate, which path will it take? A, B or C? Why?


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?

Stirring Sand, part 2

In part one, I left you with a challenge. We put a little sand into a glass of water and stirred it. Instead of moving to the outside edge, as we might expect, the sand gathered in the center of the glass. I left you with the challenge of telling me why.

Congratulations! Several of you got the right answer, and several more got it at least partially right.