Once the students are finished, add excitement to the balsa wood tower engineering project with a competition for the tower that holds the most weight. By having a goal in mind as they build, the students feel like they have something to work towards.
Start by measuring and weighing each tower to make sure they qualify. If a tower doesn't meet the specifications, it can be disqualified from the competition. This is also a great time to grade the students on their projects by looking at their creativity but also making sure they followed instructions and worked within the given guidelines.
To test the towers, use a square block slightly bigger than the opening in the top of the towers with a metal hook connected to it. This metal hook then connects to another metal hook on the handle of a five-gallon bucket. The tower balances on the edges of two tables so the bucket hangs freely from the tower between the tables.
Slowly add sand evenly to the bucket until the tower snaps or breaks in some way. Disconnect the bucket from the tower and use a basic scale to weigh the bucket of sand. The tower that holds the most weight wins and the student may receive extra credit.