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 news magazine "Maclean's", Brian Bethune praised Hanson's storytelling, writing, "For all the intriguing science, what really livens up Hanson's passionate discussion of his 'natural miracle' are the stories he tells." Laurence A. Marschall, a physics professor at Gettysburg College, wrote in a review published in the magazine "Natural History", "In sum, "Feathers" is an impressive blend of beauty, form, and function." Frances C. James, in a review published in "The Condor", described the book as "scholarly and enjoyable", commenting that "Hanson has worked hard to summarize the science behind our current understanding of the form and function of feathers, their