Activity: Toothpick Bridges
Theme: Engineering
Ideal Group Size
Grade Level
Set Up/Clean Up Time
Activity Time
Any
2-6
5 min./10 min.
10 – 30+ minutes
Math/science questions addressed: What makes a stable bridge?
Overview: Participants act as civil engineers as they design and build a toothpick bridge and test its
strength using pennies as weights.
Materials: For each group: 30-50 toothpicks, 1 lump of play dough, pennies, bridge pictures
Pitsco.com
Sample bridge design
To do: Show participants one of the bridge pictures provided.
Ask: What do you observe about it? What is it made of? What is keeping this bridge stable? What shapes
do the beams on the bridge make?
Explain: Participants will be making bridges out of toothpicks and playdough. Demonstrate how to
connect toothpicks by sticking them in to small balls of dough.
To do:
1. Invite participants to build their own bridges (this can take anywhere from 5 to 20 minutes)
2. Test completed bridges by resting the sides of the bridge on two chairs, and then placing
pennies one by one on the center of the bridge. Have them count how many pennies the bridge
can hold before it breaks.
Ask: How could you redesign your bridge to make it stronger (If time is flexible, students can try this
out)? What designs were the most successful? What shapes did you make to create a stable bridge?
Explain: Civil engineers use crossbeams to create triangles, which make a more stable bridge design.
Look for the triangles on bridges that you pass in your neighborhood!
Clean-up: Have each group take apart their bridges and re-combine play dough. Collect all pieces.
Activity extensions: for older groups
A) After the first bridge is built and tested, redesign the bridge so that it holds more weight.
B) Remove toothpicks from an existing bridge, but keep the bridge as stable as it was before.
Engineers usually have to work around budget/resource restrictions!
C) Make the bridge longer, but still keep it as stable as it was before.
Background:
Civil engineers design, build, and maintain structures like roads, bridges, canals, dams, and
buildings.The weight of materials traveling over a bridge has the effect of bending/bowing the bridge
downward, which causes compression and tension forces in the bridge beams. The various bridge
designs and new materials that engineers have developed have been driven by the need to reduce this
effect of load on the bridge, and to withstand the elements and challenges of costs and environmental
factors.
Triangles are an important shape in bridge building. Their unique strength lies in that each
side of the triangle is braced by the two other sides. Unlike a square, which can be deformed into a
diamond shape, triangles maintain their shape as long as their sides remain the same length.
These 2014 Summer Learning science activities were developed by Pacific Science Center