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Van der Waals force
Van der Waals forces are forces that act between electrons or molecules. They are named after the Dutch scientist Johannes Diderik van der Waals (1837-1923). These forces are relatively weak, and do not include forces due to covalent bonds or electrostatic interactions. Van der Waals forces can be classified:
- Forces that act between two dipoles, named Keesom after Willem Hendrik Keesom
- Forces that act between a dipole, and a charged molecule, named Debye after Peter Debye
- Forces that act between two polarised particles, called London forces after Fritz London
Geckos can climb vertical surfaces: The underside of their feet is covered with very small hairs. Each hair can only transmit a very small force, but because there is a large number of these hairs the total force is sufficient for the animal to walk on ceilings and climb vertical surfaces. The forces involved are about 250 N.