Lifting a car with two phone books
Astonishingly, it turns out to be practically impossible to separate two interleaved phone books by pulling on their spines, however much force is applied. It is even possible to suspend a car from them.
Using a model that reproduces the traction and friction forces involved, researchers have shown that when the spines of the interleaved phonebooks are pulled on vertically, part of the vertical force is converted into a horizontal force that presses on the sheets. The pages then remain stuck together due to friction.
The work, which began as a result of a challenge on the program On n'est pas que des cobayes on the France 5 TV channel, will be published in January 2016 in the journal Physical Review Letters, and is already available on ArXiv.
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Close-up of the interleaved phone books. Credit: France 5/2P2L -
Experimental device used in the laboratory to measure the friction force. Credit: Frédéric Restagno et Christophe Poulard
More information: Self-amplication of solid friction in interleaved assemblies, arxiv.org/abs/1508.03290
Journal information: Physical Review Letters
Provided by CNRS
