作者：Helhes
鏈接：https://www.zhihu.com/question/22554470/answer/21861499
來源：知乎
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維基百科條目：Friction（請無視中文版，機翻的你有本事上谷歌你有本事開門啊！）

The elementary property of sliding (kinetic) friction were discovered by experiment in the 15th to 18th centuries and were expressed as three empirical laws:

• Amontons' First Law: The force of friction is directly proportional to the applied load.

• Amontons' Second Law: The force of friction is independent of the apparent area of contact.

• Coulomb's Law of Friction: Kinetic friction is independent of the sliding velocity.

即所謂滑動摩擦三定律：1.摩擦力與正壓力成正比；2.摩擦力無關接觸面積；3.摩擦力無關滑動速度。
——————————————（分割線是這么打的么）———————————————-—
不理想的狀況下，比如摩擦生熱改變了接觸面性質——比如冰塊摩擦表面融了一層水膜，就會減小摩擦力——但是，這是不是冰塊自身的摩擦系數改變了？
如果非要說表面鍍水膜的冰塊還是冰塊，并作為整體考慮，那摩擦系數就算是變了吧。