What it shows
Balance uses signals from the eyes, the inner ear, and the muscles and joints. Taking away the vision signal makes balancing much harder, which shows how the senses work together.
The science
The brain keeps the body upright by combining vision, the vestibular system in the inner ear, and sensors in muscles and joints. Closing the eyes removes one input, and a soft cushion confuses the foot sensors. Balance time falls when inputs are removed, and practice helps the brain to improve.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A stopwatch
- A flat floor with a mat
- A folded towel or a cushion as the unsteady surface
- A notebook
- A friend near for safety
- A wall to hold if needed
Safety
For this project: Stand next to a wall or have a spotter ready to catch you, and keep the floor clear of objects. An adult supervises. This is not a medical test for balance.
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.
Choose a standing leg and note which leg you choose.
Stand on one leg on the floor with hands on hips and start the stopwatch.
Stop the timer when the lifted foot touches the floor or you hop, and write the time, to a maximum of 60 seconds.
Do this three times with eyes open and calculate the average.
Repeat with eyes closed, three times, with a spotter ready.
Repeat with eyes open standing on a folded towel.
Collect results from five volunteers and make a table.
Draw a bar chart for the three conditions and compare.
What you should see
Balance time is longest with eyes open on the floor and much shorter with eyes closed or on the soft surface, for almost every volunteer.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Which organ in the ear helps with balance?
The semicircular canals and other parts of the inner ear.
2Why is it harder with eyes closed?
The brain loses vision, one of its main balance inputs.
3Why does a wide stance help?
It gives a larger base for the centre of mass.
4How can you get better at balance?
By regular practice, as athletes and dancers do.
Take it further
Train for two weeks, five minutes daily, and plot your balance time every day.
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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