题目内容

钓鱼岛（The Diaoyu Islands）自古就是我国固有领土，它到温州市直线距离为356km，若某天我国海监船为维护我国对钓鱼岛主权，早上8：00从温州出发去钓鱼岛巡航，航行了480km，历时8时20分到达钓鱼岛，下列说法中正确的是（　　）

A、8：00是指时间间隔

B、8时20分是指时刻

C、改海监船位移大小为356km，路程为480km

D、由于海监船比较大，所以不可能将它看成质点

分析：时间间隔是指时间的长度，在时间轴上对应一段距离，时刻是指时间点，在时间轴上对应的是一个点；
位移是从初位置到末位置的有向线段，路程为轨迹的实际长度；
在物体的大小和形状不起作用，或者所起的作用并不显著而可以忽略不计时，我们把近似地把该物体看作是一个具有质量大小和形状可以忽略不计的理想物体，称为质点．

解答：解：A、8：00出发，指的是一个时间点，因此为时刻，故A错误；
B、历时8时20分，用了一段时间，为时间间隔，故B错误；
C、位移是从初位置到末位置的有向线段，为356km；路程为轨迹的实际长度，为480km，故C正确；
D、该海监船在海上航行时，确定位置时其大小可以忽略不计，故可以将该海监船看成质点，故D错误．

点评：本题关键明确位移与路程、时间间隔与时刻、质点的概念，要掌握了时刻在时间轴上对应的是一点，而时间间隔在时间轴上对应的是一段．

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【小题1】According to the author, parents and grandparents

A．didn’t have to overcome difficulties when in their teens.

B．don’t fully understand the pressures of being a teenager now

C．can easily deal with things such as choosing friends and shoes.

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A．Because he was afraid that he had lost his friends.

B．Because he and his friends weren’t in the same school.

C．Because he was too busy to be with his friends.

D．Because his friends refused to hang out with him.

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【小题4】In the letter the author mainly tells us that

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B．changes sometimes cause hurt and confusion

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