Many forces are at work on towers. Gravity and the dead load of the tower push down, the ground pushes back up, and small air movements push from the side. A foundation distributes the load into the surrounding ground material and can help balance the sideways wind force. The size of the foundation depends on the strength of the supporting ground. A foundation placed in rock can be smaller than a foundation placed in sand or mud.
Challenge your students this week to build the tallest tower they can. You can use any materials you like, such as blown up balloons, uncooked spaghetti or newspapers and tape. Remind students to think all the ways they can alter the materials they are working with. Encourage them to think about shapes and stability. Reinforce that this is not a competition between groups, but rather a chance to learn from others' discoveries so that looking at what other groups are doing is good. Remind them that they may use the tape to stiffen the materials such as paper, particularly at the base, or to hold stable shapes such as triangles or columns together.
As groups finish and measure their towers, everyone should be encouraged take a group tour of the results, thinking about the creations in terms of what forces are affecting these towers. The dead load of the tower are pushing down, the surface is pushing back up, and small air movements are adding forces from the side. What different solutions did groups come up with to counteract these forces? What is similar about the taller structures? Encourage students to point out creative uses of shapes, fastening techniques, wide bases, and other solutions to balancing and stiffening their towers.