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But there has to be kinetic friction somewhere, and indeed there is—it’s between the wheel axles and the car itself. To rotate, the axle has to slide along some surface in the housing that holds it in place. But with roller bearings and lubrication, μk can be massively reduced, from 0.56 for dry steel on steel to something like 0.002.。关于这个话题，新收录的资料提供了深入分析
。关于这个话题，新收录的资料提供了深入分析
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所以我觉得，能和他共事是一种很幸运的事。他是我们这个时代最伟大的创业者之一。。业内人士推荐新收录的资料作为进阶阅读