newton's laws

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.


These are ripple marks in beach sand, made by the wind. Similar ripples can be seen in deserts, and even in large playground sandboxes. What causes the ripples to be so evenly spaced?

Sail Fans

I got the idea for this experiment while driving around town. We were driving across the Bridge of Lions in St. Augustine, and I pointed out a sailboat that had a large fan-like propeller sticking up behind the sail. The propeller is attached to a generator, using the wind to recharge the batteries. We joked about it being a fan to provide wind if the breeze died down, which lead to a discussion about what would happen if you tried that. That lead to this experiment.

To find out what would happen if you did mount a big fan to blow on the sails, you will need:

Stirring Sand

I ran across the idea for this week's experiment (which is really more of a challenge), while researching another question. The more I thought about it, the more I liked it. It involves the unusual behavior of sand in a glass of water.

Newton's Laws

This time we will investigate Newton's laws of motion. While Galileo laid the foundations for them, Newton was the one that put them into the form that we know them today.


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?

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.