What it shows
A paper rocket is pushed off by a puff of air, and its fins keep it pointing straight. Changing only the fin shape while keeping everything else the same is a fair test of how fins help flight.
The science
Air pushed from your lungs shoots the rocket forward. Without fins the rocket tumbles because air pushes unevenly on its sides. Fins at the back make drag that pulls the tail behind the nose, so the rocket stays pointed forward, like the feathers on an arrow.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A normal drinking straw to blow through (launcher)
- A sheet of paper and a pencil to roll the rocket body, which slides loosely over the straw and is closed at the top
- Paper cut into 3 fin shapes: triangle, rectangle and no fin
- Tape and scissors
- A measuring tape
- A notebook for results
Safety
For this project: Do not aim at faces. Use a new, clean straw for each person and keep the launching area clear of others.
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.
Step 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.
Roll paper round a pencil into a tube 15 cm long and tape it, then slide out the pencil; the tube must slide loosely over the launching straw.
Fold and tape the top of the tube closed to make a nose cone, so that air blown through the straw pushes the rocket off.
Make three identical rockets, one with triangle fins, one with rectangle fins and one with no fins.
Draw a launch line on the floor and a measuring tape straight out from it.
Hold the straw at the same angle, about 30 degrees, for every launch and blow with the same breath.
Launch each rocket five times and measure the distance to where the nose first lands.
Write all 15 results in a table and find the average for each design.
Make a bar graph of the averages and pick the best design.
What you should see
The finned rockets usually fly straighter and farther than the one without fins. The table and bar graph let you decide which fin shape was best.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01What do fins do?
They keep the rocket pointing straight by making drag at the tail.
02Why test each design five times?
One launch can be a fluke, and averages are fairer.
03Which things must be kept the same?
Rocket length, launch angle, and strength of the puff.
04What is the variable being changed?
The fin shape.
Take it further
Test the number of fins, using two, three and four of the same size.
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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