Путин освободил от должности помощника секретаря Совета безопасности14:49
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One last cool thing. There’s yet another type of friction called rolling friction. You see this on a truck with rubber tires: Under the weight of the vehicle, the tires flatten out on the bottom. So when the truck is moving, the tires are continually being deformed and returning to their proper shape. This flexing heats up the tires, and where there’s heat there’s energy loss. Since energy is conserved, this means the wheels slow down, and the truck has to burn more fuel to maintain its speed. Trains, on the other hand, have very little rolling friction, because their steel wheels barely deform at all. This makes trains a more energy-efficient mode of transportation.。业内人士推荐手游作为进阶阅读
Dan Tehan says Australia ‘doing our bit to keep the region safe’. Follow updates live