题干

一带电油滴在场强为E的匀强电场中的运动轨迹如图中虚线所示,电场方向竖直向下。若不计空气阻力,则此带电油滴从A运动到B的过程中,下列判断正确的是(     )

A:油滴带正电

B:A点电势高于B点电势

C:油滴的重力势能增加,电势能减少

D:油滴的动能可能不断减小

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答案(点此获取答案解析)

C

同类题2

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    Many Years ago three soldiers,hungry and tired of battle,came upon a small village.The villagers,suffering a bad harvest and the many years of war,quickly hid what little they had to eat and met the three in the village square, shaking their heads and sighing,"Well,we are starving."The soldiers communicated with each other quietly and then the first soldier turned to the villagers.“Your poor fields have left you nothing to share,so we will share what little we have: the secret of making soup from stones.”

    Naturally the villagers were intrigued and soon a fire was built to the village's greatest pot,and then the soldiers dropped in three smooth stones.

    “Now this will be a fine soup,”said the second soldier,"but a handful of salt and some parsley(香芹)would make it wonderful!"Up jumped a villager,crying “What a piece of luck!I've just remembered where some has been left!”

    And off she ran,returning with parsley.As the pot was boiling,the memory of the villagers improved: soon carrots,beef and cream had found their way into the great pot.They ate and danced and sang well into the night, thrilled about the feast and their new-found friends.In the morning the three soldiers awoke,finding all the villagers standing before them.At their feet lay a bag of the village's best bread and cheese.“You have given us the greatest gift,”said an elder,“and we shall never forget.”The third soldier turned to the crowd,and said,“There is no secret,but this is certain: people working together can accomplish great things.”At last the light dawned on villagers.Off the soldiers wandered,down the road.

同类题3

阅读下面的文言文,完成后面小题目。

    包拯,字希仁,庐州合肥人也。知天长县。有盗割人牛舌者,主来诉。拯曰:“第归,杀而鬻①之。”寻复有来告私杀牛者,拯曰:“何为割牛舌而又告之?”盗惊服。

    徙知端州,迁殿中丞。端土产砚,前守缘贡,率取数十倍以遗.权贵;拯命制者才足贡数。岁满,不持一砚归。

    召权知开封府,迁右司郎中。拯立朝刚毅,贵戚宦官为之敛手,闻者皆惮之。人以包拯笑比黄河清,童稚妇女,亦知其名,呼曰“包待制”。京师为之语曰:“关节不到,有阎罗包老。”旧制,凡讼诉不得径造.庭下。拯开正门,使得至前陈曲直,吏不敢欺。中官势族筑园榭,侵惠民河,以故河塞不通,适京师大水,拯乃悉毁去。或持地券自言有伪增步数者,皆审验劾奏之。

    迁谏议大夫、权御史中丞。奏曰:“东宫虚位日久,天下以为忧,陛下持久不决,何也?”仁宗曰:“卿欲谁立?”拯曰:“臣不才备位乞豫建太子者为宗庙万世计也陛下问臣欲谁立是疑臣也臣年七十且无子非邀福者。”帝喜曰:“徐当议之。”请裁抑内侍,减节冗费,条责诸路监司,御史府得自举属官,减一岁休暇日,事皆施行。

    张方平为三司使,坐买豪民产,拯劾奏罢之;而宋祁代方平,拯又论之;祁罢,而拯以枢密直学士权三司使。欧阳修言:“拯所谓牵牛蹊田而夺之牛,罚已重矣,又贪其富,不亦甚乎!”拯因家居避命,久之乃出。其在三司,凡诸管库供上物,旧皆科率外郡,积以困民。拯特为置场和市,民得无扰。吏负钱帛多缧②系,间辄逃去,并械.其妻子者,类皆释之。迁给事中,为三司使。数日,拜枢密副使。顷之,迁礼部侍郎,辞不受,寻以疾卒,年六十四。赠礼部尚书,谥孝肃。

    拯性峭直,恶吏苛刻,务敦厚,虽甚嫉恶,而未尝不推以忠恕也。与人不苟合,不伪辞色悦人,平居无私书,故人、亲党皆绝之。虽贵,衣服、器用、饮食如布衣时。尝曰:“后世子孙仕宦,有犯赃者,不得放归本家,死不得葬大茔③中。不从吾志,非吾子若孙也。

(节选自《宋史·包拯传》)

【注释】①鬻:(yù)卖。②缧(léi):捆绑犯人的绳索。③茔:(yíng)墓地。