Our January Engineering Challenge theme was roller coasters. Before we started, I talked a little bit about momentum, demonstrating that a marble rolled along a mostly flat track will stop, but a marble rolled down an inclined track will keep going, and that marble rolled down a very steep track can build up enough momentum to keep going even uphill. Most of the children nodded along, as this was all well within their life experience of how balls interact with the world.
Once they had the general idea, I gave them the first challenge: to build a roller coaster that allowed the marble to go up and over a hill. I purposefully make my first level of challenge relatively simple so that every child participating will have at least one success by the end of the program. To accomplish their challenge the children were given pipe foam that I had cut in half lengthwise, forming a channelled track. The pipe foam was perfect for our purposes: very flexible for young hands to manipulate and very cheap at at about $1 for a 6 ft tube, which provided 2 channels. I also gave them access to lots of tape. I had regular masking tape and also painter’s tape, which I 
emphasized needed to be used if the children were going to use the wall as part of their building process. (And here I’d like to put in a plug for painter’s tape. It’s more expensive than regular masking tape, but otherwise so much better! Unlike masking tape it never takes the paint off the walls. It’s also much easier to peel off the roll, a problem we’ve had with several different brands of masking tape. It’s almost as sticky as masking tape, and I’ve successfully used it to hold posters up on the wall for as long as I wanted the poster to stay up.)
We had about thirty kids working on the challenge, mostly in small groups and pairs. There were a significant number of dads with their children, which is always exciting to see. I love watching the parents get involved with the engineering, and the great discussions the parent/child interactions produce. The kids are often more accurate in their predictions of what will happen! Maybe because they have spent more time messing around with similar materials?
Our second level of challenge was to create a loop-the-loop. This was significantly harder, but everyone got there eventually. I like to emphasize that engineering requires a lot of trial and error. I did not see any frustration, all of the participants were confident that just one more tweak to the design would yield results.
I told the children who completed the second challenge that they could either do a free design, or they could try for two loop-the-loops. Most chose to try for two loops. One thing I noticed during this program was that it was not enough for the children to accomplish the task: they needed me to be a witness to their success. This meant running around the room quite a bit so that I could personally watch marbles rolling around the tracks. The looks of delight were definitely worth it.
