Put a box of spaghetti and a roll of scotch tape on the table and tell your students to construct a cantilever that extends as far as possible. The structure must be attached to the top of the table and may not be attached to anything else. Measure the length of the cantilever and send in your pictures! If you want this to be even more challenging, build the longest cantilever that can support a box of cereal.
To learn more about cantilevers, go here.