题目

如图，一质量m=1×10﹣6kg，带电量q=﹣2×10﹣8C的微粒以初速度v0竖直向上从A点射入一水平向右的匀强电场，当微粒运动到比A高2cm的B点时速度大小也是v0 ， 但方向水平，且AB两点的连线与水平方向的夹角为45°，g取10m/s2 ， （1） AB两点间的电势差UAB； （2） 匀强电场的场强E的大小． 答案：解；由A到B动能定理得： UABq−mgh=12mv02−12mv02=0 解得：UAB=-10V 解；将微粒的运动分解为水平和竖直两个方向：水平方向做匀加速运动，竖直方向做竖直上抛运动．设A、B沿电场线方向的距离为d．则有 竖直方向 h=v0+u2t水平方向 d=v0+02t解得 h=d=0.02m所以匀强电场的电场强度大小为 E=Ud=100.02V/m=500V/mHands play an important part in our daily life. But do you know which of your two hands you use more? Very few people use both hands equally well.  Most of us are right-handed.  Only about five people out of a hundred are left-handed.  New-born babies can take hold of things with either of their hands, but in about two years they usually use their right hands.  Scientists don’t know why this happens.Monkeys are our close relatives in the animal world. Scientists have found that monkeys like to use one of their hands more than the other, but it can be either hand.  There are as many right-handed monkeys as left-handed ones.  Next time you visit a zoo, watch the monkeys carefully, you will see that some of them will use their right hands and others will use their left hands.  But most of the people use their right hands better and this makes life difficult for those left-handed people.  We live in a right-handed world. 【小题1】How many people among 100 people use their left hands better? A. 5%.     B. 50%.     C. 95%. 【小题2】What’s the meaning of the underlined word “equally” in Chinese? A. 公正地    B. 均等地    C. 平凡地【小题3】New-born babies can use  ____  ____ __. A.  both of their hands    B.  neither of their hands    C.  their right hands【小题4】Which of the following is true? A.  There are more monkeys using their right hands than left hands. B.  There are more monkeys using their left hands than right hands. C.  There are as many right-handed monkeys as left-handed ones. 【小题5】“We live in a right-handed world. ”means ____ ____ __. A.  Most people use their right hands better. B.  Few people use their right hands better. C.  Half of the people use their right hands better.