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Heat can also be produced by the impact of imperfectly elastic bodies as well as by friction. This is the case, for instance, when we produce fire by striking flint against steel, or when an iron bar is worked for some time by powerful blows of the hammer.

不完全弹性体的冲击和摩擦也能产生热。这是一个例子，例如，当我们用燧石打钢而产生火的时候，或者当一根铁棒被锤子猛击了一段时间而产生火的时候。

— Hermann von Helmholtz 亥姆霍兹