如图所示,带正电小球质量为m=1×10-2 kg,带电荷量为q=1×10-6 C

题型:问答题

问题:

如图所示,带正电小球质量为m=1×10-2 kg,带电荷量为q=1×10-6 C,置于光滑绝缘水平面上的A点.当空间存在着斜向上的匀强电场时,该小球从静止开始始终沿水平面做匀加速直线运动,当运动到B点时,测得其速度vb="1.5" m/s,此时小球的位移为s="0.15" m.求此匀强电场场强E的取值范围.(g取10 m/s2)

某同学求解如下:设电场方向与水平面之间夹角为θ,由动能定理qEscosθ=mvB2-0,得E== V/m,由题意可知θ>0,所以当E>7.5×104 V/m时小球将始终沿水平面做匀加速直线运动.

经检查,计算无误.该同学所得结论是否有不完善之处?若有请予以补充.

考点:电场强度的定义式
题型:问答题

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题型:问答题

阿拉伯人属于[ ]

A.黄色人种

B.黑色人种

C.白色人种

D.混血种人

题型:问答题

阅读下面短文,按照句子结构的语法性和上下文连贯的要求,在空格处填入一个适当的词或使用括号中词的正确形式填空。

No One Dares to Help

On a recent Sunday, I was buying groceries in a supermarket 小题1:  ___     I heard the sound of a car accident. It was close but not very close, so I continued shopping. As I took a right turn on Munadhama Street, I saw a man 小题2: ____    (lie) on the ground in a small pool of blood. He wasn’t dead.

小题3: ____       idea of stopping to help or to take him to a hospital crossed my mind, but I didn’t dare. Cars passed without stopping. Pedestrians and shop owners kept doing 小题4:  __________     they were doing, pretending nothing 小题5:_____________ (happen).

I was still looking at the injured man and blaming myself 小题6:           not stopping to help.    小题7:      ______ shoppers peered at him from a distance, sorrowful and sympathetic, but did nothing.

I was on to another grocery store, staying for about five minutes while shopping for tomatoes, onions and other vegetables. During that time, the man managed to sit 小题8:_____________ and waved to passing cars.

No one stopped. No one did 小题9: ______     . No one lifted a finger.

The injured died on the street. The only reaction came from a woman 小题10:   ______    was in the grocery store. In a low voice, she said,” My God, bless his soul.”

An offer of aid could have saved the man’s life.

题型:问答题

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B.雨热不同季

C.盛行西北风

D.盛行东南风

题型:问答题

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B.目视测量法

C.徒步测量法

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