Towers - Background
I found this to be a great end of the year project when the kids are wiggly and not able to focus anymore on bookwork. They thoroughly enjoy the competitive nature of the challenge and get very involved in designing, building and redesigning their structures.
The student handout provided gives the criteria that I assigned to my students as well as a grading rubric. Briefly, the structures must meet the following requirements:
- The building must fit on the base.
- The building must be at least 36 cm tall.
- The building must have 2 stories that are each at least 18 cm tall (approximately the height of 1 straw).
- Each story must support the weight of at least 1 sand bag (250 grams) without collapsing.
- A construction drawing with measurements and analysis must be submitted before earthquake testing.
- To survive an earthquake test, the building must not collapse for 10 seconds after the earthquake begins. The weights must stay on the building.
I observed the structure after each stage of testing described below. If at any point the structure buckled to the point that the sandbags fell off or dropped by more than halfway to the ground (a sandbag on the first story 18 cm high can fall as much as 9 cm and still be considered passing while a sandbag on the second story 36 cm off the ground can fall 18 cm) the structure was considered to have failed that stage of testing. Students had 2 minutes to repair any damage to their structure between each stage of testing although no new straws or materials could be provided.
- Place 1 sandbag on the first story.
- Place 1 sandbag on the second story.
- Minor earthquake with 1 sandbag on the top story. I designated that moving the platform horizontally to the side so that it touched the frame started a minor earthquake. No vertical motion was involved.
- Major earthquake with 1 sandbag on the top story. I designated that moving one corner of the platform so that it touched the corner of the frame as well as the table below started a major earthquake, leading to both horizontal and vertical motion.
- Major earthquake with 1 sandbag on the top story and 1 sandbag on the first story.
- Major earthquake with 2 sandbags on the top story and 1 sandbag on the first story.
- Major earthquake with 2 sandbags on the top story and 2 sandbags on the first story.
- Continue major earthquakes adding 1 sandbag at a time, first to the top story, then to the first story.
The best structure in my classes survived until a major earthquake with 4 sandbags on the top story and 3 sandbags on the first story.
None, although the activity fits well among the seismology lessons.