Science Lesson Kit · Teacher Resource
Bridge Engineering: Designing for a Load — 5E Lesson Plan
Physical Science · 50 minutes
Grade 3
5E lesson flow
01
Engage
6 min
Teacher Does
Show two same-material bridge models that perform differently.
Students Do
Notice structural differences and predict where each may fail.
Ask
- What is different about the shape or connection?
Look For
Design features rather than material quantity.
02
Explore
16 min
Teacher Does
Guide teams through a controlled load test.
Students Do
Build within constraints, add loads consistently, and record the first failure point.
Ask
- What stayed the same?
- Where did failure begin?
Look For
Controlled span and load placement.
03
Explain
9 min
Teacher Does
Connect failure points to engineering evidence.
Students Do
Mark the failure location and propose one targeted redesign.
Ask
- What evidence tells you where to improve?
Look For
Failure-location evidence.
04
Elaborate
12 min
Teacher Does
Require one redesign variable and a retest.
Students Do
Change one design feature and compare results to the first trial.
Ask
- Did the change improve the success criterion?
Look For
Same criteria across trials.
05
Evaluate
7 min
Teacher Does
Assign the bridge-test audit.
Students Do
Interpret a new data set and propose a fair next test.
Ask
- Which variables must stay controlled?
Look For
Transfer of fair-test reasoning.
Student goal
I can test a bridge prototype fairly and use a failure point to improve the design.
Learning objectives
- I can identify the load, supports, and span in a bridge model.
- I can carry out a fair bridge test by controlling important variables.
- I can use a failure point as evidence to improve a bridge design.
Materials
- Index cards or cardstock
- Craft sticks if used consistently
- Masking tape
- Two equal supports
- Ruler
- Cubes or pennies used as loads
- Data sheet
Before class
- Set one standard span such as 20 cm.
- Set a material limit for every team.
- Choose a lightweight, repeatable load such as cubes.
- Mark the exact load placement point.
- Define failure as a clear bend limit, slip, or collapse before testing.
Prior knowledge
- Forces can change motion or shape.
- A fair test controls important variables.
Vocabulary
- structure
- Something built from connected parts to support a purpose.
- load
- A force or weight that a structure must support.
- support
- A part that holds up or stabilizes a structure.
- span
- The distance a bridge crosses between supports.
- prototype
- A model built to test a design idea.
- failure point
- A place where a tested design bends, slips, breaks, or stops meeting the goal.
Differentiation
- Provide pre-cut equal material sets.
- Use a bridge-parts visual with support/span/load cues.
- Offer the frame: It failed at ___. I will change ___. I will keep ___ the same.
- For extension, ask students to compare strength with a material-use constraint.
Assessment
- Check controlled variables.
- Check accurate load counts.
- Check failure-point record.
- Check redesign is tied to evidence.
Exit ticket
Your bridge bends in the middle at 15 cubes. Name one design change to test and two conditions you would keep the same.
Extension
Add a second design criterion, such as using less material while still meeting a target load.