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Yo-Yos by John, Kevin and Minna

YO! We love yo-yos! When we're doing tricks, one of the most important things to master is making our yo-yos "sleep." Sleeping is when you throw the yo-yo just right, let it reach the end of the string and spin it around the axle. It just sort of hangs out there. Since we want to master our tricks, we asked this DragonflyTV question: How does the length of the yo-yo string affect its "sleeping time?"

What did we do?
We tested three strings: 24, 36, and 48 inches. Our goal was to make our yo-yos sleep for as long as possible. We each tested the different string lengths three times and found the average sleep time for every length of string. We tried to keep the force of our throws consistent.

What did we find out?
It was hard to throw the yo-yo on the long string without letting it hit the ground. Still, when we did get the long-string yo-yo to sleep, it slept longer than the other two lengths. The shortest string gave us the shortest sleep time. We thought it was because the long string let the yo-yo rotate more times as it unwound.

What can you do?
• There's a lot of science in simple toys, even a top. Make a simple top out of heavy papers and a pencil or toothpick. Try to find a design that spins a long time without tipping over. Try long and short pencils or different shapes of paper. Test other variables, like the mass of the top. Record your results and think about why certain designs spin better than others.

• Grab a book about yo-yos and check out a few more tricks. Create an investigation similar to the DFTV kid scientists', but with a different trick and variable. Does a heavier yo-yo help you "walk the dog" longer? Do plastic yo-yo's beat wood when it comes to "going around the world?"

• Use Newton's Laws to make a milk carton spin. Carefully poke a hole in the top of a paper milk carton (right in the center) and tie one end of the string around the hole. Carefully poke holes in the bottom right of each side of the milk carton. Keep the carton over a sink or tub. Then pour water into the carton. The water will shoot out of the bottom holes. Hold the carton by the string over the sink, and watch the carton spin. Now make a science investigation out of it. What happens if you make the holes bigger? What if you start with a new carton and put the holes on the bottom left? What if you put the holes in the middle? Keep track of all your results!

• Use this physics investigation as a science fair project idea for your elementary or middle school science fair! Then tell us about it!

 Go to the DFTV Boards, and tell us about your science investigation.

What game was invented in 1931 by an unemployed architect?