On a hot day, an electric fan is just the thing to cool you down! Can you make a fan from KNEX, that spins fast enough to cool you?
Levels of difficulty:
Level 1 - Make a fan that turns when you spin it by hand Level 2 - Make a fan that spins with a spring motor Level 3 - As level 2, with a switch to turn it on once the spring motor is wound up
Equipment: KNEX set, plus a K'NEX spring motor.
Approach: How could you make the blade of the fan from KNEX rods and connectors? Can you make a frame to hold up the blade while it spins? For level 2, how could you attach a spring motor to your model? For level 3, usually when you wind up a spring motor and let it go, it spins straight away. Can you add some sort of lever or switch to your model that will stop it turning until you want it to?
The aim of the project is to build a model in which the turning blades of a fan create a wind. To demonstrate that winding up a spring motor stores energy, and that letting it go releases energy
Possible solution: See photo.
Before starting: If possible, demonstrate a working electric fan.
Conclusion: Firstly, draw a diagram showing the forces involved and all moving parts. Then write a description of how the force applied during the winding-up process is transferred to the spring and stored there, and then how on release the forces are transferred to create a wind. Finally, consider why a fan makes you feel cooler.