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Getting Started Select Design Task Learn About Design
MOVIE 1:  6 minutes 11 seconds
 
Shopping Bag

The Shopping Bag task is a signature redesign task for the Stuff That Works! curriculum. The activity has three phases (see Movie 1): collecting and classifying bags, loading bags and noticing where and how they fail, and then redesigning and testing them. (Find the complete task in Packaging & Other Structures, pages 44-56, or a newer version on the STW! project website: http://citytechnology.ccny.cuny.edu/Design_Packaging.html.)
The task draws upon students' prior experience with shopping bags -- you will find them more prepared than usual when doing this redesign activity.

DITC's Shopping Bag section holds the following:
  •  How Shopping Bags Work  Learn about stresses on bags as structures that support loads, forces and how they concentrate in materials, and what to look for to predict where failures are likely to occur.
  •  Bag Types & How They Fail  Review three main types of shopping bags and then watch slow-motion movies showing different bags being loaded until they fail. You can use these movies with your students to develop diagnostic reasoning and focus their attention on areas of potential weakness in different bag designs.
  •  Bag Redesign  Describes 3 way students redesign shopping bags, including: making the materials stronger through reinforcement, distributing load more broadly, and changing areas weakened by poor design.
  •  Shopping Bag Video Timeline  View scenes of the shopping bag task being used in two Atlanta classrooms and a Stuff That Works! teacher professional development workshop held in Los Angeles in 2003.
  •  Designing Your Lessons  Gives tips for making your lesson plans and provides sample questions and a movie to check for student understanding.

Materials List and Handouts
  • Collection of bags (found during scavenger hunts)
  • Masking tape - 3/4" or 1" wide
  • Rolls of pennies as loads for bag (can be secured from most banks, and then returned without cost)
  • Clothesline for string handles (or other wide cord or ribbon)
  • Brown paper lunch bags (for redesign work)
  • Roll of brown paper, manila folders (optional, used as additional support materials)
  • Scissors
  • Shopping Bag pages (from Stuff That Works! website)
Connections To Standards

Science students can control variables (like bag materials and features) and design experiments during Phase 2 or 3 of the shopping bag task. Students learn about the forces of tension, compression and shear - to understand how bags work and where and how they fail. They use test results when making their design decisions.

Math students can calculate the surface area (materials used) of their bags, and the volume their bags hold. They reason about tradeoffs when optimizing the ratio of Costs and Benefits (Materials Used / Load carried or Volume created). Materials selection becomes important when costs are considered. Giving students the option to add one square foot of paper, in any shape, could require them to calculate areas of materials used for reinforcement.

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