如图所示为一列沿着x轴正方向传播的横波在t=0时刻的波形图．已知

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问题选择题

如图所示为一列沿着x轴正方向传播的横波在t=0时刻的波形图．已知这列波的周期T=2.0s．则（　　）

A．这列波的波速v=2.0m/s

B．在t=0时，x=0.5m处的质点速度为零

C．经过2.0s，这列波沿x轴正方向传播0.8m

D．在t=0.4s时，x=0.5m处的质点的运动方向为y轴正方向

答案

A、由图知：波长λ=1m，则波速v=

m/s=0.5m/s．故A错误．

B、在t=0时，x=0.5m处的质点位于平衡位置，速度不是零而是最大．故B错误．

C、过2.0s，这列波沿x轴正方向传播距离为x=vt=0.5×2m=1m．故C错误．

D、t=0.4s=

T，图示时刻x=0.5m处的质点正向上运动，故t=0.4s时，x=0.5m处的质点的运动方向为y轴正方向．故D正确．

故选D

阅读理解

Education is very important for the development of China. As we know, China has the largest population in the world and most of them live in the countryside. Because of the economic（经济）conditions, many families are very poor, especially those in the remote（偏僻的）areas, and they can’t afford to send their children to school. Many children have to stop attending school. Project Hope is aimed at solving this problem so that every child of school age can receive a regular education.

Project Hope mainly depends on the contributions（捐款）of the urban（城市的）people and overseas Chinese who care about the development of China’s education. The contributed（捐赠）money will be distributed（分配）by Project Hope council to the countryside to help the children who can’t afford the education. One hundred yuan will help such a child finish his primary education.

Project Hope is a good way to improve the education in the rural（农村的）areas, but it isn’t enough. So far, only a small part of the children benefit（受益）from it. So we should pay more attention to the problem and do much more to help raise the educational level of the country.

根据短文内容判断正（A）误（B）。（10分）

小题1:In the remote areas many poor families can’t afford their children’s regular education.

小题2:Project Hope only depends on the contributions of the urban people and overseas Chinese.

小题3:Project Hope aims to afford an education for the poor children.

小题4:One hundred yuan will help a poor child finish his primary education.

小题5:So far, most part of the children have benefited from Project Hope.

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填空题

俗话说：“人往高处走，水往低处流。”水总是从高处流向低处是因为水受到力的作用，这个力的方向是。

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