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问题 选择题

一匀强电场的电场强度E随时间t变化的图象如图所示，在该匀强电场中，有一个带电粒子在t=0时刻由静止释放，若带电粒子只受电场力作用，则下列说法中正确的是（　　）

A．带电粒子只向一个方向运动

B．0～2s内，电场力做正功

C．2s末带电粒子回到原出发点

D．4s末带电粒子回到原出发点

答案

带电粒子在t=0时刻由静止释放，在0-1s内带电粒子沿着电场力方向做匀加速直线运动，

1-2s内沿原方向做匀减速直线运动，2s末速度减为零；

2-3s内沿反方向做初速度为零的匀加速直线运动，

3-4s内继续做匀减速直线运动，4s末速度减为零，回到出发点．

A、由上分析可知，带电粒子做往复运动．故A错误．

B、0～1s内电场力做正功，1～2s内电场力做负功．故B错误．

C、D，2s末带电粒子离原出发点最远，4s末带电粒子回到原出发点．故C错误，D正确．

故选D

阅读理解

Australia has an unusual kangaroo—although he is a pet, he lives like a man. He is dressed in clothes, likes watching TV and drinking, also eats bread, plays football and does some exercise.

His name is Bi Muer. Months ago, a 50-year-old woman, Julia Bradley adopted (收养) him. He now lives a happy life. Every morning, he can enjoy delicious bread and later watch TV with his "mom". In the afternoon, he can go to the garden and play football and in the evening, he can drink while watching TV.

In the beginning, Muer was only 20cm tall, but now, he can easily jump over a one-meter fence.

小题1: The kangaroo likes______________.

A. watching TV and drinking B. seeing a movie   C. playing basketball

小题2:Who adopted the kangaroo?

A. Bi Muer. B. Julia Bradly.    C. Bill Smith.

小题3:What can the kangaroo do every morning?

A. Drink.  

B. Go to the garden.

C. Enjoy delicious bread and watch TV.

小题4:How tall was the kangaroo in the beginning?

A. 10cm.    B. 20cm.    C. 30cm.

小题5:The passage is mainly about    .

A. An unusual kangaroo 

B. An Australia woman

C. A kangaroo' s hobbies
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填空题

计算型填空：

①在980g水中加入20gSO2，完全溶解后所得溶液溶质质量分数为______

②在葡萄糖（C  4H12O6、）淀粉[（C4H10O3）8]、聚乙烯[（C2H4）8]三种物质中，与等质量碳元素相结合的氢元素的质量比为______

③一个碳酸分子中的质子总数是______，一个AlP

 2-4
离子中的电子数是______

④向某硫酸溶液中加入BaCl2到不再反应为止，产生沉淀的质量和原硫酸溶液的质量相等，则原硫酸溶液中溶质的质量分数为______%（BaSO4式量为233）

⑤在t℃时，100g水中加入mgNa2SO2或加ngNa2SO2•7H2O，均可使溶液达到饱和，则m和n的关系式正确的是：m=______（用含有n的代数式表示）
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