No matter how much force is applied (within reason, no hammer of Thor stuff) you can't separate two interleaved phone books by pulling on their spines.

A new experiment shows it is even possible to suspend a car from them.

Using a model that reproduces the traction and friction forces involved, researchers at the Laboratoire de Physique des Solides (CNRS/Université Paris-Sud), Laboratoire Gulliver (CNRS/ESPCI ParisTech), Laboratoire de Génie des Procédés Papetiers (CNRS/Grenoble INP) and McMaster University in Canada 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. 

© France 5/2P2L.

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 7 January 2016 in the journal Physical Review Letters, and is already available on ArXiv.

Citation: Self-amplication of solid friction in interleaved assemblies. Hector Alarçon, Thomas Salez, Christophe Poulard, Jean-Francis Bloch, Elie Raphaël, Kari Dalnoki-Veress, and Frédéric Restagno. Physical Review Letters, 7 january 2016. ArXiv :