Rolling Can Race

Setup

1. Wipe each can clean and dry with a towel
2. Place cans on their sides on a flat, smooth surface
3. Make sure the surface is clean (dust and moisture can reduce the effect)
4. Inflate balloons and tie them off

Instructions

1. Charge the balloon by rubbing it on hair or wool for 10–15 seconds until it wants to stick to your hand.
2. Hold the charged balloon 1–2 inches from the side of the can (no touching) and watch the can roll toward it.
3. Keep the balloon just ahead of the can to “lead” it across the table; recharge with a quick rub if it slows down.
4. Race: everyone gets a can and balloon, set a finish line, and guide your can across without touching the can or table.

Tips for Success

• Dry conditions work best - humidity reduces static electricity
• Charge frequently - re-rub the balloon if the effect weakens
• Hair works great - especially dry, clean hair
• Keep the balloon close but not touching the can
• Smooth surfaces like laminate tables work better than rough wood

What's Happening?

Static Electricity Basics:
When you rub the balloon on your hair or wool, you're creating static electricity through a process called triboelectric charging.

How Rubbing Creates Charge: When you rub the balloon on hair or wool, electrons move onto the balloon. That gives the balloon a negative charge while your hair becomes slightly positive. Bringing the charged balloon near the metal can pushes the can's electrons away from that side, leaving a slightly positive area that the balloon attracts. This pull—called electrostatic induction—makes the can roll without any touching. Humidity or letting the balloon touch the can will drain the charge and the effect fades until you recharge the balloon.

Advanced Experiments

1. Test different materials for rubbing:
2. Hair vs. wool vs. fleece vs. cotton

3. Which creates the strongest charge?

4. Try different objects:

5. Can you move a ping pong ball?
6. What about a plastic bottle?

7. What about a steel can vs. aluminum?

8. Measure the distance:

9. How far away can the balloon be and still attract the can?

10. Does a bigger charge allow longer distances?

11. Humidity experiment:

12. Try this on a dry day vs. a humid day
13. Why does humidity make it harder?