newton's law and friction

newton's second law：
After object stress, its momentum rate of change, with the net force which its receives (i.e. is proportional with joint forces), and is in the unidirection.
Newton third law of motion:
When two object correlations, each other works hard to devote oneself to mutually uses in opposite party, both size is equal, the direction is opposite, but affects on the different thing function body. This law is called “the function and the law of reaction”.

Solid friction
Two solid surface rub mutually. If two solid surface's choice of material improper or between them exerts mutually the pressure is big, then the solid friction will create the attrition. Will not use in the situation which the lubricant or the lubricant will expire to create the solid friction.

Mixed friction
Insufficient or the movement start can present the mixed friction in the lubricant. By now the rubbing surface some areas immediate contact. The mixed friction creates the attrition must be smaller than the solid friction. Should avoid the mixed friction under the long time movement's condition, but the mixed friction is often tolerated in the technical project.