骑自行车时，用力蹬车，车会向前运动加快，当不再用力时，车会慢慢停下来．这个现象是否与牛顿第一定律相矛盾？
不矛盾．牛顿第一运动定律研究的是物体不受力（合力为零）时的运动规律；物体受力（合力不为零）时，物体的运动状态将要改变．车加快向前是由于受人蹬车力的作用，车慢慢停下来是受地面摩擦力的作用，他们都是受合力不为零运动状态改变的具体表现，与牛顿第一定律并不矛盾．
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| On Sunday, I 1 at 7:00. I 2 breakfast at 3 . Then I help my mother with her housework. At about 9:00 I 4 home. I do some shopping 5 bike. At about 11:00, I 6 my bike back home. I like cooking very much. We have lunch at 11:30. In the afternoon, I 7 the train to a movie. It takes me two hours 8 it. We have supper at 6:00. In the evening, I 9 my homework. My parents 10 newspapers. We go to bed at about 10:00. | ||||
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