A balloon-powered CD hovercraft is a simple school project that shows how air can make objects glide more easily. You build it from a CD, a pop-top bottle cap, a balloon, and a little glue. When the balloon releases air through the cap, the air spreads under the CD and lifts it slightly above the tabletop.
This makes the hovercraft fun to test and a great way to learn about friction and motion.
Key Facts
- Friction is a force that opposes motion when surfaces rub against each other.
- An air cushion reduces contact between the CD and the table, so friction becomes smaller.
- Pressure = force / area, or P = F / A.
- Newton's third law says that for every action force, there is an equal and opposite reaction force.
- A wider, smoother base helps the hovercraft spread air more evenly under the CD.
- The hovercraft works best on a smooth, flat surface because less air leaks unevenly.
Vocabulary
- Hovercraft
- A vehicle or model that floats on a cushion of air above a surface.
- Friction
- A force that resists motion when two surfaces touch or rub against each other.
- Air cushion
- A thin layer of moving air that supports an object and reduces contact with the surface below.
- Pressure
- The amount of force spread over a certain area.
- Thrust
- A pushing force that can move an object forward, backward, or in another direction.
Common Mistakes to Avoid
- Using too much glue around the cap, because extra glue can block the opening where air needs to flow.
- Forgetting to seal the cap tightly to the CD, because leaks around the cap reduce the air cushion under the hovercraft.
- Testing on carpet or a rough table, because rough surfaces create more friction and make the hovercraft harder to move.
- Blowing up the balloon and releasing it before the cap is closed, because the air escapes too early and the hovercraft cannot build a steady air cushion.
Practice Questions
- 1 A balloon contains enough air for the hovercraft to glide for 12 seconds. If it travels 180 cm in that time, what is its average speed in cm/s?
- 2 The CD has an area of 110 cm2 and the air cushion pushes upward with a force of 2.2 N. What is the average pressure under the CD in N/cm2?
- 3 Explain why the same hovercraft usually glides better on a smooth tabletop than on a carpet.