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现象一:把一个木块放到桌面上,我们怎么吹也吹不动。就是在木块下垫几支铅笔,把它和桌面的摩擦改为滚动摩擦,我们也很难一口气吹走它。再把这木块放进盛了水的脸盆里,使木块浮在水面上,我们再向它吹一口气,则木块就会被吹跑了。为什么木块放在水里便容易吹跑呢?现象二:我们都知道,如果给自行车的车轴里涂上润滑油,则自行车骑起来就变得轻些。这又是为什么呢?现象三:我们还都知道,在北方的冬天,穿着冰鞋在冰面上溜冰,若轻轻一蹬,就会滑得很远很远,而若在水磨
Phenomenon one: put a piece of wood on the desktop, how do we blow can not blow. Is a few pieces of pencil under the wood block, the friction between it and the desktop changed to rolling friction, it is difficult for us to blow it away. Then put the wooden block into the water in the basin, so that pieces of wood floating on the water, we blow to it again, then the wood will be blown away. Why is it easy to blow wood in water? Phenomenon 2: We all know that if a bike’s axle is coated with grease, the bike gets lighter. Phenomenon 3: We also all know that in winter in the north, wearing skates ice skating on the ice, if a gentle pedal, it will slide very far away, and if the water mill