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3. Physical period: Uniform circular motion is a kind of periodic motion. The so-called periodicity refers to the fact that after a certain period of time, the moving object repeats back to its original position, and the instantaneous speed repeats back to its original size and direction. The time it takes for an object to move in a uniform circle is called a period. The period is expressed by the symbol T, and the period is also a physical quantity describing the speed of uniform circular motion. The long period indicates the slow motion of the object, while the short period indicates the fast motion of the object.Basically, made up其时正当暮春三月，江南海隅，一个三十来岁的蓝衫壮士。高易道：好的，臣会着手处理的。一部分人认为应该主动出击，用人海淹死他们。讲述以冷冬冬为代表的几个小学生，父母都在外地打工，只好跟着爷爷、奶奶生活，冷冬冬家里只有奶奶，生活、学习就更困难了。孩子们想妈妈，想坐火车到滨哈市去看妈妈，因为超过1米1需要买火车票，所以他们千方百计不想长高。后来，一位老列车长偶然得知情况后，答应有条件带他们去看妈妈。为了达到老列车长允许去看妈妈所要求的学习成绩，几个孩子以此为动力互相帮助，冷冬冬的学习成绩有了很大进步。在影片的结尾，冷冬冬因为数学成绩比老列车长所要求的少了一分，主动放弃了和同学一起坐火车去滨哈市看妈妈的机会，而是决心要沿着铁道线走到滨哈市去看妈妈.