Monday, February 22, 2010


Here’s today’s science project. This one comes from the book Guide To the Best Science Fair Projects by Janice VanCleave.

The question is: What makes a satellite orbit around the earth?

We used two pieces of paper, a cardboard tube, piece of tape, food coloring, water, a marble, a piece of clay, and a cookie sheet.

Tape one end of the tube at the corner of the cookie sheet.

Lay the piece of paper at its edge.

Put several drops of food coloring into a glass with a bit of water, and stir it.

Put the marble (a large marble left more visible tracks for us) into the raised end of the tube, and notice its path across the paper.

Raise the long side of the tray (the side near the tube) about an inch, and prop it up with a book or bits of clay.

Wet the marble again, and send it through the tube.

This time it makes a much rounder orbit!

The reason is because first there was only the weight of the marble to pull to the earth, but the second time there was also the gravity of the tray…. if you raise it again, you get a different path again.

Trev wanted it to fall almost straight down from the tube, so we had to decide how to do that! :)

So we discovered that a satellite needs two things to stay in orbit – the forward-moving motion of the satellite (the engine), and the gravity pulling it toward the center of the earth. Without gravity, the satellite would travel in a straight line, and without the force of the motion of the satellite, it would smack into the earth!

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