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Material Strength Bridge Investigation

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Material Strength Bridge Investigation

A creekside walking track needs a small bridge. Investigate whether a bridge deck made from folded newspaper or paper straws can hold more load. Work safely with a partner, follow the steps, and use evidence to explain your recommendation. You will need newspaper, paper straws, sticky tape, two sturdy supports, a small cup and identical counters or weights.

Plan a fair test

Build each bridge to span the same gap (20 cm). Make both decks the same length and width, using the same deck design for each material. Use the same amount of tape and the same cup. Add one identical counter at a time to the centre of the bridge. Stop when the bridge touches the surface below or collapses. Repeat each material three times, rebuilding it each time. Change only the material used for the deck. Record the maximum number of counters held.

1.Before testing, predict which bridge material will hold more counters: folded newspaper or paper straws. Explain one reason for your prediction.

2.Which feature of the investigation is the independent variable—the factor you deliberately change?

The deck material
The number of counters added
The 20 cm gap between supports
The amount of tape

3.Name two things you must keep the same to make this a fair comparison.

4.Explain why each bridge should be tested three times rather than just once.

Results from another team

A team tested both materials using the same procedure. Their results are shown below. Use this data for Questions 5–8.

Material

Trial 1

Trial 2

Trial 3

Folded newspaper

Paper straws

5.Calculate the mean (average) load for the folded-newspaper bridge. Show your calculation: (8 + 10 + 9) ÷ 3.

6.Calculate the mean load for the paper-straw bridge. Show your calculation: (12 + 11 + 13) ÷ 3.

7.How many more counters did the stronger material hold on average? Use the means from Questions 5 and 6.

8.Which material was stronger in these tests? Give one piece of numerical evidence from the results.

Conclusion and next steps

Use the results as evidence, but remember that a conclusion from one team's model test does not prove that the material will behave the same way in every real bridge.

9.The team's prediction was that newspaper would be stronger. Were the results consistent with that prediction? Explain using the data.

10.Recommend one material for the model bridge and write a conclusion that uses evidence from the trials. Then suggest one change for a new investigation and state what you would keep the same.