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有这样一则谚语让人印象深刻:山会成为你的阻力,但可以挖隧道;水会成为你的阻力,但可以架桥梁;悬崖不会成为你的阻力,但会让你粉身碎骨。运动中最直观的阻力就是摩擦力,无论是各种车辆、舟船或是飞行器,都要通过改变形状、提高动力效率等各种方式,来减小摩擦力的影响。然而,下雪天路面结冰的时候,轮胎上却要拴上铁链增加摩擦力,防止车辆打滑。同样,轮
It’s impressive to say that mountains can become your resistance, but tunnels can be made; water can be your resistance, but you can bridge it; the cliffs will not be your resistance, but will make you crushed. The most direct resistance to exercise is friction, whether it is a variety of vehicles, boats or aircraft, have to change the shape, improve power efficiency and other means to reduce the impact of friction. However, when the snowy road pavement is frozen, the tires have to be fastened with iron chains to increase the friction and prevent the vehicle from slipping. Again, round