Building Big Educator's Guide Mini-Activity Human Arch, Forces
Initial Publication Date: August 25, 2009
Summary
Summary – In this physics/engineering activity students physically make an arch by pushing on each other with arms outstretched over head. As long as the pair of students balance each other's force their arch will stand, although it will be weak. If one student stops balancing the force, the arch will fail. Their arch strength can be improved by adding students acting as buttresses which push in at the base where the arches are pushing out.
CollapseLearning Goals
Concepts
1. Forces pushing on each other can be balanced and keep objects at rest.
2. Unbalanced forces cause motion and/or change in the direction of motion of an object.
Vocabulary: force, arch, buttress, Goals 2-3
1. Forces pushing on each other can be balanced and keep objects at rest.
2. Unbalanced forces cause motion and/or change in the direction of motion of an object.
Vocabulary: force, arch, buttress, Goals 2-3
Context for Use
Intermediate classroom, any size class, even numbers of students is convenient. This classroom activity can be done in 10 minutes. Students should know that a force is a push or a pull and should be able to observe where the pushes are taking place on their bodies as they make their initial arch and the second one with buttresses. No special materials are needed.
Description and Teaching Materials
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BUILDING BIG
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Mini-Activity: Human Arch
Activities Index | Glossary Educator Support
Definition Arch: A curved structure that converts the downward compression force of its own weight, and of any weight pressing down on top of it, into a force along its curve. This results in an outward and downward force along the sides and base of the arch.
Buttress A side support that counteracts an outward pushing force, the way bookends keep books on a shelf from sliding sideways. Buttresses are often used to support the sides of arches and tall cathedral walls, where they counteract the outward thrust.
1. Have two kids form an arch by placing their palms together and leaning toward each other, sliding their feet as far back as they can. Caution them not to lose their balance. Ask: Where do you feel a push or a pull? (pushing on their hands)
2. Have a third kid gently pull down on the top of the arch to test its strength. Ask: How difficult is it to break the arch? (not difficult)
Illustration: kids forming an arch. 3. Have the group brainstorm ways for two more kids to join the arch and make it stronger, but without breaking up the space beneath the arch. Guide them to the idea of adding buttresses by asking the arch-makers how stable their legs feel. Then repeat Step 2 and compare the results. (The buttresses exert an inward force on the sides of the arch that balances the outward force created by the load pressing down on the top of the arch.)
Video Connection "Roman Bridges" from Bridges (see the Program Description)
Try the Shapes Lab.
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This Web site was produced for PBS Online by WGBH.
Web site © 2000-2001 WGBH Educational Foundation.
BUILDING BIG
Bridges
Domes
Skyscrapers
Dams
Tunnels Spacer image with 5 links within the image
The Educators Guide
How to use this guide
Program Descriptions
Planning Ideas
To Activities
Additional Resources
Buy the Video
Mini-Activity: Human Arch
Activities Index | Glossary Educator Support
Definition Arch: A curved structure that converts the downward compression force of its own weight, and of any weight pressing down on top of it, into a force along its curve. This results in an outward and downward force along the sides and base of the arch.
Buttress A side support that counteracts an outward pushing force, the way bookends keep books on a shelf from sliding sideways. Buttresses are often used to support the sides of arches and tall cathedral walls, where they counteract the outward thrust.
1. Have two kids form an arch by placing their palms together and leaning toward each other, sliding their feet as far back as they can. Caution them not to lose their balance. Ask: Where do you feel a push or a pull? (pushing on their hands)
2. Have a third kid gently pull down on the top of the arch to test its strength. Ask: How difficult is it to break the arch? (not difficult)
Illustration: kids forming an arch. 3. Have the group brainstorm ways for two more kids to join the arch and make it stronger, but without breaking up the space beneath the arch. Guide them to the idea of adding buttresses by asking the arch-makers how stable their legs feel. Then repeat Step 2 and compare the results. (The buttresses exert an inward force on the sides of the arch that balances the outward force created by the load pressing down on the top of the arch.)
Video Connection "Roman Bridges" from Bridges (see the Program Description)
Try the Shapes Lab.
Building Big Home | Site Map | Labs | Databank | Glossary
Bridges | Domes | Skyscrapers | Dams | Tunnels
Local Wonders | Who Builds Big? | Educators' Guide | Shop
This Web site was produced for PBS Online by WGBH.
Web site © 2000-2001 WGBH Educational Foundation.
Teaching Notes and Tips
This is a fun activity that your students will enjoy. I clear a space in my classroom by pushing tables aside. My students like to see how strong their arch can be. They add buttresses and have another student pull down on their arch!
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Assessment
Students will draw an arch (bridge) with buttressesn and indicate with arrows where the forces are pushing in and out.
Standards
Science Standard 09
6th grade
2. Physical Science
2. Motion
2. Understand that Forces have magnitude and direction and govern the direction of an object.
1. Recognize that when forces acting on an object are balanced, the object remains at rest or continues to move at a constant speed in a straight line, and that unbalanced forces cause a change in the speed or direction of the motion of an object.
6th grade
2. Physical Science
2. Motion
2. Understand that Forces have magnitude and direction and govern the direction of an object.
1. Recognize that when forces acting on an object are balanced, the object remains at rest or continues to move at a constant speed in a straight line, and that unbalanced forces cause a change in the speed or direction of the motion of an object.