Slinky Science - Combining Geometry and Science

"What walks down stairs, alone or in pairs, and makes a slinkity sound? A spring, a spring, a marvelous thing! Everyone knows it's Slinky."

If you're singing along, then you probably already know, that Slinkies don't really walk down stairs, alone or in pairs. At least not as easily as they did in those commercials from the '70s (click the link to watch one, if you have no idea what I'm talking about - everyone should know the joy of a Slinky).

In fact, I was pretty happy to find a Slinky science experiment this week, that involved finding the best angle of an inclined plane to walk a Slinky down. Not only, because it incorporated some of the geometry skills we've been developing, but also because I've always wanted to see a Slinky "walk" down a plank, or stairs, in person. It was one those life challenges I didn't manage to master as a child.

Ideally, the experiment is to be done with two Slinkies of different sizes. You measure the diameter, of each Slinky, and then find the best angle of incline to use for getting the most "steps" per second, out of each Slinky. After scouring half of western Montana for Slinkies, we did manage to find two, but they were both the same size.

However, that still gave us the opportunity to measure the angle of incline of our plane, which in this case, was the back side of a leaf from our table.

And, even with one size of Slinky, there was still plenty of room for the children to make some interesting observations. Like the fact, that each of our thinner encyclopedias added to our stack, increased our angle by one degree.


After a few goes, at different angles, with one child manning the slinky, one measuring angles, on recording, one watching the time, and the two youngest demanding a turn, we thought 18 degrees seemed to be the best angle of incline for our board, to achieve maximum Slinky walking speed, which for us was 2 "steps" per second (really 8 steps in 4 seconds, which the children simplified).

Our board was pretty slick though, and often the Slinky slid to the bottom, after only a few steps.

I asked the children for solutions, and they decided we needed to add friction between the board, and the Slinky. So, we taped on a few pieces of felt, and tried all the angles again.


After confirming our original findings, but with a great deal more ease, the older children started to experiment with changing the depth, and rise of our stairs, to get the Slinky to walk down them.


They were getting close to success, when they realized it was time to go to meet up with some friends, and the younger children ran off with both Slinkies. It became immediately apparent, that two slinkies, and three children is not a good equation. I removed C, to watch a favorite movie, and then after a while, went back to check in on E (age 6), and D (age 9).

Who, I was happy to discover, had started their own "stairs" experiment. They weren't succeeding, but they were having a great time, changing variables, and testing hypotheses, which sounds like science to me.


For more fun with science check out this week's Science Sunday link up at Adventures in Mommydom.

It's great to be a homeschooler.