Materials List (for each group):
- 1 bag of spice drops
- 1 cup of mini marshmallows
- 1 box of round toothpicks (250 count)
For the challenge, students must build a 2-foot long bridge that is at least the height of a toothpick that can hold a 3 pound weight placed in the center of the bridge. Once they have accomplished that, they must raise the bridge off the table or desk and have it suspended over air for a span of six inches. The height the bridge is raised can vary, but using two identical textbooks on either side of the bridge is practical.
Be aware that spice drops and gum drops, while generally allergen free, are often processed in facilities that handle nuts, dairy, wheat and soy, so allergies can be an issue. My sensitive students were able to wear gloves to protect their skin. For alternatives and allergen free options, check out this list at Sure Foods Living.
For the super accurate scientific model of The Weather Weasel, I filled a white men's tube sock with rice until it weighed 3 pounds (the approximate weight of my ferret). This weigh presents a fun challenge, not just because of the weight, but because it's floppy and molds itself to the bridge. It also requires a wider bridge than students might normally choose to make when they are focused on the length of the bridge. This is good, because a wider bridge is more stable. If you don't have a super accurate scientific model available, try stacking books on the bridge instead.
With younger students, have them focus first building a sturdy structure directly on a flat surface. They may not get past that point, and that's just fine. Have them focus in on the shapes they use: triangle versus square, pyramid versus cube. Encourage students to "prototype" a small span of bridge before committing to a larger length.
And just in case you hear, "That's impossible!," let me assure you it is not. Here are some awesome pictures of past creations!
Want to learn more about bridges? Check out "Building Big" by PBS.