Year 7 Technology · 2026
Week 10 · Lesson 19

Dry-run + final repairs

Week 10 · 75 minutes · Year 7 Technology (Mandatory) · Bridge It

TE4-3DPTE4-8EN

🎯 Learning intentions

  • I can conduct a safe dry-run load test at low weight.
  • I can identify and repair weak spots before the real test.
  • I can predict which part of my bridge will fail first.

✅ Success criteria

  • Bridge has been through a dry-run with a 500 g load.
  • Any weak spots identified in the dry-run have been reinforced.
  • My folio has a PREDICTION — which member I think will fail first and why.

Do Now · 5 min

Prediction time. In your folio:

  1. How much weight do you predict your bridge will hold at failure? (guess in grams)
  2. Which member do you think will fail FIRST?
  3. What shape will the failure be — snap, buckle, or joint separation?

I Do · ~10 min Teacher demonstration

Teacher demo — dry-run procedure.

  1. Position bridge across the 350 mm gap on two desks.
  2. Hang the bucket from the centre of the deck.
  3. Start empty. Add 250 g (1 cup of sand). Wait 10 seconds. Observe.
  4. Add another 250 g. Observe.
  5. Stop at 500 g — this is DRY RUN, not to failure.
  6. Remove bucket. Inspect bridge for cracks, separation, deformation.
  7. If weak spots found — reinforce NOW with PVA + clamp.
WHS: 1 m exclusion zone. Teacher operates bucket. Students observe. Report any cracking noises to teacher.

We Do · ~15 min Guided practice

First pair's dry run with Ms Gao. Whole class watches. We analyse what happens together.

You Do · ~35 min Independent pair work

Your dry-run + repairs (35 min).

  1. Set up bridge on dry-run bench.
  2. Teacher will watch and call commands. You follow.
  3. Observe 500 g dry-run.
  4. If bridge is fine → celebrate; prep for L20.
  5. If bridge shows weakness → PVA + clamp + masking tape immediately. Will have 1 day for full cure before L20 test.
  6. Update journal: "Dry run result: ___. Repairs: ___."

Differentiation

🪜Support

Teacher does whole dry-run. Student observes and records.

🎯Core

Student loads bucket with teacher supervision.

🚀Extension

Load bridge to just below predicted failure to get max signal — propose the weight stop point yourself.

Exit Ticket · 5 min

  1. Did your bridge pass dry-run?
  2. Any repairs needed? What?
  3. Final prediction for failure load — in grams?

📚 Resources for this lesson

Before you leave Quick check-in

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