force and interactions

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.

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Magnets
OK, a puzzle this time. Imagine that you have two steel bars that look alike. One is a magnet and the other is not. Without using anything else (No paperclips, iron filings, etc.) how would you be able to tell which is the magnet?

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