The Classroom Shake-Platform Challenge

Compare model designs that could reduce earthquake hazards.

Investigate the Models

Read the investigation. Use the graph to compare the designs.

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.

Which claim is supported by all four bars?

A. Every added safety part stopped all block falls.
B. None of the tested designs stopped every block fall.
C. The designs all had the same number of block falls.
D. The plain model had the fewest block falls.

How many fewer block falls did the anchored model have than the plain model across three trials? fewer block falls

Select the two comparisons supported by the graph.

Adding a wide base reduced block falls by 6 compared with the plain model.The anchored model had twice as many block falls as the wide-base model.The anchored-plus-lip model had more block falls than the wide-base model.The anchored-plus-lip model had 16 fewer block falls than the plain model.

Ignore supply points for this question. Which tested design best reduced block falls?

A. Plain
B. Wide base
C. Anchored
D. Anchored plus lip

A team claims that anchoring worked better than widening the base in these tests. Do you agree? Support your answer with results for both models.

Choose with Limits

Use both the test results and the supply points. A design must meet every limit in a question.

Which design meets the class's goal of no more than 6 block falls and no more than 4 supply points?

A. Anchored: 6 block falls and 3 supply points
B. Wide base: 12 block falls and 2 supply points
C. Anchored plus lip: 2 block falls and 6 supply points
D. Plain: 18 block falls and 0 supply points

What trade-off does the graph and supply information show when a team adds a lip to the anchored model?

A. It uses 3 fewer points but has 4 more block falls.
B. It uses 6 more points but has 2 fewer block falls.
C. It uses 3 more points but has 4 fewer block falls.
D. It uses 2 more points but has 6 fewer block falls.

Ellis says, "The anchored-plus-lip model had only 2 block falls, so it will stop every object from falling in any earthquake." What is the best correction?

A. The model stopped every fall because 2 is a small number.
B. The model reduced falls in these tests, but did not stop them all.
C. The model must have failed because any fall makes a design useless.
D. The model proves that earthquake shaking can be stopped by a shelf.

The class wants to find out how much a lip helps without anchors. They will compare a plain model with a lip-only model. Select the two steps that make this a fair comparison.

Start both models with ten identical blocks in the same marked positions.Move the tray farther when testing the plain model.Use the same tray movement and number of trials for both models.Use a shorter shelf for the lip-only model.

Use Evidence Carefully

Think about what the models show, what still needs testing, and how the evidence could guide a decision.

10.

Why can't these tests alone tell how a real classroom shelf will perform in a strong earthquake?

A. Real shelves, objects, and earthquake shaking can differ from the models.
B. A small model always shakes more strongly than a real classroom.
C. Repeating a model test removes all differences from real earthquakes.
D. Counting fallen blocks tells nothing about the tested designs.

11.

The class proposes using stronger tape straps on the anchored model. What should they do before claiming that the stronger straps work better?

A. Choose the stronger straps because their name proves they work.
B. Reuse the old results because both designs include straps.
C. Test the new straps once with fewer blocks on the shelf.
D. Compare both strap types in repeated tests with other conditions unchanged.

12.

The school wants to use the model findings to help plan real shelf safety. Which next step is best?

A. Have students shake a real shelf to check whether it tips.
B. Use classroom tape on real shelves because it worked on cardboard.
C. Ask qualified adults to choose attachments suited to the real shelves and walls.
D. Leave real shelves unchanged because a model cannot provide useful clues.

13.

A new model display has a budget of 6 supply points. Its goal is no more than 3 block falls across three trials. Recommend a tested design. Use its block-fall result and supply points to explain why it fits better than the anchored design without a lip.