What it shows
A strip of paper with two folded wings spins as it falls, because air pushing on the slanted wings makes it turn. Longer wings catch more air and slow the fall, while adding paper clips makes it fall faster. Air resistance is a real force.
The science
As the helicopter falls, air pushes up on the wings. The wings are folded in opposite directions, so the air pushes each one sideways in a different direction and the whole thing spins. The spinning wings sweep out a large area, so there is a lot of air resistance pushing up against gravity, which is why the fall is slow. Longer wings mean more area and more resistance, so a slower fall; extra paper clips mean more weight pulling down, so a faster fall. The same balance of weight and air resistance decides how fast a parachute or a falling seed comes down.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A few sheets of used paper (free)
- Scissors
- Paper clips
- A ruler
- A stopwatch or phone timer
- A chair or a staircase to drop from safely
Safety
For this project: Drop from a chair only with an adult holding it steady, and never lean over a stair railing.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Cut a strip of paper about 20 cm long and 5 cm wide.
Cut down the middle from the top for 8 cm to make two wings, and fold them in opposite directions.
Make two small cuts near the bottom on each side, fold the sides in and fold the bottom up to make a stem; add one paper clip to hold it.
Drop it from a measured height, such as 2 metres, and time how long it takes to reach the floor; it should spin on the way down.
Time three drops and take the average, since one drop can be unlucky.
Make two more helicopters the same but with wings of 6 cm and 10 cm, and time three drops of each.
Go back to the 8 cm helicopter and add a second and then a third paper clip, timing three drops each time.
Make a table and two bar charts: fall time against wing length, and fall time against number of clips.
What you should see
The helicopters spin as they fall. Longer wings give a slower fall, with the 10 cm wings taking the longest, and each extra paper clip makes the fall quicker.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Why does the helicopter spin?
The air pushes on the two wings, which are folded opposite ways, so it turns.
2Why do longer wings fall more slowly?
They have more area, so there is more air resistance holding them up.
3What does adding a paper clip do?
It adds weight, so gravity pulls harder and the fall is faster.
4Which seed falls like this in nature?
Maple or sycamore seeds spin down the same way so that the wind can carry them.
Take it further
Try the same helicopter made from thin paper, thick card and a plastic sheet, and see which falls slowest.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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