Mechanical energy nonconservative forces, like frictional forces, will be present, but often they are of negligible values and the mechanical energy's being constant can therefore be a useful approximation. In elastic collisions, the mechanical energy is conserved but in inelastic collisions, some mechanical energy is converted into heat. The equivalence between lost mechanical energy (dissipation) and an increase in temperature was discovered by James Prescott Joule. Many devices are used to convert mechanical energy to or from other forms of energy, e.g. an electric motor converts electrical energy to mechanical energy, an electric generator converts mechanical energy into electrical energy and a
Feathers: The Evolution of a Natural Miracle is "something for everyone to learn", from professional ornithologists to non-biologists. Bostwick warned scientific readers, however, that "Feathers" uses poetic license "to adapt some of the historical accounts a little to make them flow as stories" and that "Hanson uses a few analogies to explain some of the more complex biological phenomenon that are not entirely accurate." Feathers: The Evolution of a Natural Miracle Feathers: The Evolution of a Natural Miracle is a 2011 natural history book by American conservation biologist Thor Hanson. Published by Basic Books and written for general audiences, the book discusses the significance of feathers, their