A Small Model of a Classroom Hazard
An earthquake makes the ground shake. Shaking can tip furniture and make objects fall from shelves. Falling objects can hurt people nearby. Ms. Okafor's fourth-grade class wondered how different shelf designs would perform during shaking. They used small models, not real classroom furniture. No students stood near furniture to test earthquake safety.
First, teams built four cardboard shelf models of the same height, with the same shelf size. The plain model had no added safety parts. The wide-base model had extra cardboard around its bottom. The anchored model had tape straps fastening it to a cardboard wall. The anchored-plus-lip model had the same straps and a low cardboard edge along the shelf's front. A lip can block objects from sliding over that edge; straps can hold a shelf against its wall.
Next, the class placed each model on the same large tray. Each model had an identical cardboard wall firmly attached to the tray behind it. Teams placed ten identical foam blocks in marked positions on each shelf. Their teacher moved the tray sideways between two tape marks six times in six seconds. The models and blocks were small and lightweight, and everyone kept fingers away from the moving tray.
After each trial, students counted the blocks that had fallen off the shelf, including blocks that fell when a shelf tipped. They reset the model, checked its parts, and returned all ten blocks to their marked positions. They tested each design three times. The design changed, but the blocks, starting positions, tray movement, and number of trials stayed the same. The graph adds the block falls from all three trials for each design.
Finally, the class compared supply points, which represented the materials needed for each model. The plain design used 0 points, the wide-base design used 2, the anchored design used 3, and the anchored-plus-lip design used 6. For their next classroom display, the team wanted no more than 6 block falls across three trials while using no more than 4 supply points.