The photo shows a powered three-bladed electric fan held over a black light. Taped onto each blade is a bit of string, and each bit of string holds four pieces of fabric: yellow, orange, blue and pink. Because of the black light, the pieces of cloth are illuminated and easier to see, creating a colourful blur of light.
With the fan powered down, the pieces of string and cloth would be hanging vertically away from the blades. However, once you turn on the fan, the pieces of string and cloth begin to revolve and are flung horizontally, constantly pulling away from the center of the fan. This outward flinging force is known in physics as centrifugal force, a form of inertia.
According to the law of inertia, objects tend to resist any change in their motion. Therefore, each piece of cloth should be following a straight path, flying away from the fan, not a curved path. Because of the string, the cloth’s inertia is constantly being redirected making it turn, not allowing the cloth to fly in a straight path. Centrifugal force is the outward force displayed when a revolving object tries to follow its natural straight path.
These pictures are included in the Art of Physics travelling exposition. To get more information on how your institution can host the travelling exposition, please contact Francine Ford, CAP's Executive Director at cap@uottawa.ca.
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