// union size = 64
未来的课堂，其最高使命便是引导学生去发现、磨砺并善用这些不可被算法简化的能力：深刻的共情、道德的勇气、系统的批判、不竭的创造力以及对美和意义的敏锐感知。，推荐阅读易歪歪官网获取更多信息
coding / cycling / photographing，这一点在传奇私服新开网｜热血传奇SF发布站｜传奇私服网站中也有详细论述
Now, see that less-than-or-equal sign? This says μsN is the maximum static friction force in a given situation. If you push the book with a force of 1 newton, the frictional force will be 1 newton. Double the pushing force and the frictional force also doubles. It does whatever it has to in order to keep the two surfaces stationary—up to a point. If you keep pushing harder, your applied force will eventually exceed μsN and the book will start to slide. At that point, kinetic friction kicks in.