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[ Human Arch | Paper Bridge ]
Human Arch - Icebreaker Activity
Concept:
- Force
- Compression
- Load: Live and Dead
What you need:
- Five children; and
- a little floor space
How long it takes: 10 minutes (20 minutes with follow-up investigations)
Challenge: Building a human arch that doesn't break when someone pulls on it.
What to do:
- Select three kids.
- Ask two students to form an arch by extending their arms towards one another and pressing their palms against each other.
- Direct the kids to backup until they are as far apart as possible, without breaking the arch.
- Ask a third student to GENTLY pull down on the arch. (Keep the pressure on until the arch collapses.)
- Ask the "arch" what happened. Have them describe what happened to the rest of the group.
- Introduce the kids to force (a push or pull acting on an object), compression (a squeezing force pushing a material together), live load ( the weight of whatever sits on, travels over, or hangs from a structure), and dead load ( the weight of the structure itself). Ask them how this affects their bridge.
- Select two more kids. Ask the group how they could use these two kids to strengthen the arch.
- Rebuild the arch and try out their ideas.
- The kids may need help getting to the idea of creating a buttress-having the two new kids sit on the floor with their backs leaning against the calves of the students forming the arch. If they are having difficulty ask leading questions, like "how did your legs feel when 'Sally' was pulling on your arms?" or "where would you place 'Johnny and Sarah' to help strengthen the arch?"
- Once the kids have buttressed their arch, have the third child repeat pulling gently on the arch. What happens?
- Regroup the kids and ask them how hard was it to withstand the pulling in each situation? Which arch design was harder to collapse? What did you feel during the activity? How did the people sitting on the floor affect the strength of the arch? Can you identify the forces acting on the arch?
- To give everyone an opportunity to experience compression, load, and butressing break the kids into groups of five. Ask them to repeat the entire activity, switching the roles within the group of five students so everyone has a chance to play each role.
Paper Bridge - Main Activity
Concept:
- Effective use of materials
- Shape's effect on strength
What you need (per group):
- Several sheets of plain paper such as photocopier paper
- Scissors
- Ruler
- Five paper clips
- Small weights, such as metal washers, pennies, or film canisters filled with sand
- Several books to support the sides of the bridge above the ground
How long it takes: 25 minutes (40-60 minutes with follow-up investigations)
Challenge: Building the strongest bridge you can out of one piece of paper and up to five paperclips that spans 20 cm (8 inches).
What to do:
- Lead a short discussion by asking the children to describe bridges they have seen around the area. Why do we need bridges? What do the bridges look like? What are qualities a bridge should have?
- Explain that the city has asked us to make a bridge that can span a river 8 inches wide. The bridge must be made out of one sheet of paper and up to five paperclips, and cannot be attached to the table or desk.
- Holding a piece of paper and one of the weights ask how many weights they think a piece of paper can hold. Explain that their bridge must be able to support the weight of the bridge, the dead load, but also the additional weight of the washers, pennies or canisters, the live load.
- Divide the children into groups of two and have one child from each group collect the needed materials.
- Each group should think out and sketch their design before building. Once a group has completed a bridge, have them set it up across the book supports placed 20 cm (8 inches) apart. Have one of the group members place weights, one at a time, in the middle of the span until the bridge collapses. The group should record how many weights the bridge supported.
- Ask the group what influenced the design for their bridge? Where did their bridge first break when it collapsed? How could they redesign that part of the bridge to be stronger? Have the group redesign and test their bridge again. Are there similarities in the design of each group's strongest bridge?
New questions to investigate:
- If you could add one thing to make your bridge stronger what would it be? Try it and note the difference.
- How could you make a bridge that would span 30 cm (12 inches)?
- How could you design and build a structure out of paper and paper clips that will support a book at least 5 cm (2 inches) off the ground?
Students may also ask their own questions inspired by this activity.
