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:
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.
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.
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
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.
Gives tips for making your lesson plans and provides
sample questions and a movie to check for student
|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
- Brown paper lunch bags (for redesign work)
- Roll of brown paper, manila folders (optional, used
as additional support materials)
Bag pages (from Stuff That Works! website)
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.