noun, Biology. 1. an orientation of an organism to an external stimulus, as light, especially by growth rather than by movement. Origin of tropism. 1895-1900. First recorded in 1895-1900; independent use of -tropism. Related forms. tropismatic.
Friction on as-grown graphene (Fig. 1c) is ultra-low and rather uniform with its magnitude close to the previous reports4. In contrast, friction on graphene after ï¬uorination becomes
For low speeds the kinetic friction can be considered constant [1]. I am however unsure what effects dominate at higher speeds. If there's air around it then there's for example drag which causes a force proportional to $v^2$[2]. [1] http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html#kin