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自行车是同学们最为熟悉的交通工具.当你和这位“朋友”结伴上学时,有没有想到过关于它的奥秘呢?本文给你说说其中的三个. 1.前进的动力和阻力要弄清自行车前进的动力,必须先对它的结构有一定的了
Bicycles are the most familiar means of transport for students. When you went to school with this “friend”, did you think of the mysteries about it? This article will tell you about three of them. 1. The motivation and resistance to advance To understand the driving force of the bicycle, we must first have a certain structure