A balloon hovercraft is a fun school project that shows how air can help an object glide. It uses simple materials: an old CD, a pop-up bottle cap, glue, and a balloon. When the balloon lets out air, the CD can float just a tiny bit above the table.
This reduces rubbing, so the hovercraft slides smoothly.
Key Facts
- Friction is a force that slows motion when surfaces rub together.
- A thin cushion of air under the CD reduces friction with the tabletop.
- Newton's third law says that for every action force, there is an equal and opposite reaction force.
- Air pushed downward by the balloon creates an upward reaction force on the hovercraft.
- Speed = distance ÷ time, so v = d/t.
- More trapped air in the balloon usually means a longer hover time, if the cap and seal do not leak.
Vocabulary
- Hovercraft
- A vehicle or model that glides over a surface on a cushion of air.
- Friction
- A force that resists motion when two surfaces touch or rub.
- Air cushion
- A thin layer of moving air that lifts an object slightly and helps it slide.
- Newton's third law
- The rule that every force has an equal force pushing back in the opposite direction.
- Airflow
- The movement of air from one place to another.
Common Mistakes to Avoid
- Using too much glue near the CD hole can block the airflow, which stops the air cushion from forming.
- Leaving gaps around the bottle cap lets air leak out the sides, which weakens the lift under the CD.
- Testing on a rough carpet makes the hovercraft slow down, because rough surfaces create much more friction than a smooth tabletop.
- Inflating the balloon and letting it go before opening the pop-up cap will not work well, because the air must flow down through the cap and CD hole.
Practice Questions
- 1 A balloon hovercraft travels 120 cm in 6 seconds. What is its average speed in cm/s?
- 2 In three trials, a hovercraft moves for 8 seconds, 10 seconds, and 12 seconds. What is the average hover time?
- 3 Explain why the hovercraft slides farther on a smooth table than on a towel, using the ideas of airflow and friction.