问题 计算题

甲、乙、丙三物体同时同地出发做直线运动,运动情况如图所示。

(1)试分析在20 s时间内三个物体的运动情况。

(2)甲物体运动的路程是多少?

(3)丙物体的平均速度大小是多少?

答案

解:(1)由题意知三物体均做直线运动,区别在于:乙做匀速直线运动,甲做速度先减小后增大的往返的直线运动,丙做速度不断增大的单向直线运动

(2)甲物体先向位移正方向运动,通过的路程为100m,后向位移负方向运动,运动路程20m,所以甲总路程为120m

(2)丙物体的平均速度:

完形填空
完型填空。
     Zheng Tao is five years    1   . He is a lovely boy. He plays    2    other children in the small park each
day. The park is near his building.
     His mother buys new clothes for    3   . The clothes are expensive and nice. Zheng Tao feels very happy.
     "Mum, can I go out and play with my friends? I want them to    4    my new clothes," asks Zheng Tao.
     "Yes, please keep your clothes    5    "says the mother. She's going to do some cooking.
     "We'll    6    supper after your comes back. "    7    about six his father comes back from work.
Zheng Tao goes home for supper.
      "Why do you have so much earth on your clothes?    8    his mother.
      "You shouldn't    9    the nice clothes dirty." says the mother.
      "I'm sorry, Mum." says Zheng Tao,"I have   10   time to take off my clothes when I fall."
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单项选择题