Paper Bridge Engineering Experiment (Easy STEM Activity)

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This easy paper bridge experiment is a simple but powerful way to introduce kids to engineering, structural design, and material strength—using just paper and a few household items.

By changing only the shape of the paper, kids can see firsthand how engineers use design to make structures stronger without adding extra material. It’s quick to set up, hands-on, and perfect for STEM lessons, homeschool, or classroom learning.

Supplies Needed

You likely already have everything you need:

• 2 paper cups or plastic cups

• Pennies or other small weights (washers, beans, marbles)

• 1 sheet of paper (printer paper or notebook paper)

• Scissors (optional)

Engineering Challenge: Build a Paper Bridge

The goal:
See how much weight a paper bridge can hold—and how changing the shape of the paper affects its strength.

Step 1: Flat Paper Bridge (Baseline Test)

1. Cut a strip of paper about 8 inches long and 4 inches wide (exact size isn’t critical).

2. Place the two cups a few inches apart.

3. Lay the paper flat across the cups to form a bridge.

4. Slowly place pennies in the center of the paper.

5. Count how many pennies it holds before collapsing.

This is your control test.

Step 2: Folded (Accordion) Paper Bridge

1. Take the same paper strip and fold it accordion-style lengthwise.

2. Place the folded paper back across the cups.

3. Add pennies again—placing them along the folds.

4. Count how many pennies it holds this time.

Kids are usually shocked by how much stronger the folded bridge is.

Look how much stronger folding the paper made the paper bridge!

Why Does Folding the Paper Make It Stronger?

This experiment demonstrates a key engineering concept:
Shape matters more than material.

The Science Behind It

• A flat sheet of paper bends easily under weight.

• Folding the paper increases its moment of inertia (resistance to bending).

• The accordion folds create ridges, which:

  • Distribute weight more evenly

  • Reduce bending stress

  • Increase stiffness without adding material

Engineers use this same principle in:

• Corrugated cardboard

• I-beams

• Truss bridges

• Skyscraper frames

By folding the paper, you’re turning a weak material into a much stronger structure—purely through design.

Engineering Vocabulary (Optional Add-In)

• Load – the weight placed on the bridge

• Span – the distance between the supports

• Compression – forces pushing inward

• Tension – forces pulling outward

• Structure – something designed to support weight

Questions to Ask Kids

• Which bridge design held more weight? Why?

• Would a longer span make the bridge stronger or weaker?

• Does the width of the paper matter?

• What happens if you add more folds?

• Where does the bridge bend first?

Encourage kids to explain their thinking like real engineers.

Paper Bridge Variations to Try

These are perfect for extending the lesson or making it more challenging:

1. Change the Span

Move the cups farther apart. How does distance affect strength?

2. Change the Paper Type

Try:

• Construction paper

• Cardstock

• Newspaper

Which material performs best?

3. Try Different Fold Styles

• Accordion fold

• Triangle (tent shape)

• Rolled tube

Compare results.

4. Add a Weight Limit Challenge

“Design a bridge that holds 50 pennies using only one sheet of paper.”

5. Connect to Real Bridges

Look at pictures of:

• Beam bridges

• Truss bridges

• Arch bridges

Which design looks most like your paper bridge?

More Engineering STEM Activities

If your kids enjoyed this experiment, try these next:

• Make Paper Hold Up Books

• Popsicle Stick Bridge Engineering Project

• How to Make a Popsicle Stick Catapult (STEM Challenge for Kids)
• STEM Engineering for Kids: Make a Bubble Blower Machine