题干

一个质点沿半径为R的圆周运动一周后回到出发点,在此过程中,路程和位移的大小出现的最大值分别是(   )

A:2πR,2πR

B:0,2πR

C:2R,2R

D:2πR,2R

上一题 下一题 0.0难度 选择题 更新时间:2017-04-28 01:22:27

答案(点此获取答案解析)

D

同类题2

阅读下文,回答问题

读书三境界

袁利荣

    ①读书有三境界:“吞”“啃”“品”。

    ②“吞”乃生吞活剥,囫囵吞枣——是充满饥饿感的青春发奋的标志。虽然广收博采难免盲目,进食过速导致腹胀——但这个过程毕竟是日后学富五车、满腹经纶的必不可少的前奏。古今中外有许多人都是进入中年后凭“反刍”青春岁月里的泛读而成名成家的。“吞”虽为知识积累的必经之途,但毕竟是读书的低级阶段。

    ③“啃”乃咀嚼消化,强行吸收——是志存高远的人生必经的头昏脑涨、寝食不安的砥砺智慧的夜路。咬烂磨碎骨头,获取钙质,这当然谈不上享受——但却是峥嵘人生必须付出的艰辛。“为伊消得人憔悴”是任何一位学有所成的人都不能蠲(juān)免的里程。“啃”是在“吞”之基础上的知性提高——这是将死的知识化为活的血肉的过程。

    ④“品”乃焚香沐浴,如饮醍醐(tíhú,比喻使人彻底醒悟的智慧)——是成熟聪颖的心灵与星空的娓娓絮语。月下折枝、花前怜玉、豁然贯通的人生不胜惋惜地告别了青春光阴——庄严地踏上了奉献岁月。浮躁尽除,功利淡化,读书成了颐养灵性的乐事——默然回首,天机消溶于慧心。“品”是在“啃”之基础上悟性升华——这是进入人生创造之园的门票。

    ⑤读书人多如牛毛,但大多数都停留在第一境界,仅少数不甘人生庸碌者可进入第二境界。进入第三境界,非志强智达者不能。但能进入第三境界者,必是成功地穿越了第一与第二境界的人。“吞”至其博,“啃”至其深,“品”至其灵性——若无博与深,则灵性无其根本。

    ⑥举凡大家鸿儒,书读到“品”的份上后,往往将“吞”“啃”“品”三字当成进一步治学的相济并用的三种方法:“吞”文字,“啃”新意,“品”韵致。或者是:泛读的“吞”之,精读的“啃”之,需细细体悟的则“品”之。

    ⑦对一般的读书人而言,不谈三境界,如能将“吞”“啃”“品”三宇当作对待不同读物的不同阅读方法:用于消遣的书“吞”,有用的书“啃”,启心益智的书不妨“品”——那么,人生同样会受益无穷。

同类题4

阅读短文,按要求完成各题。

    I was ten when I first sat with my grandmother behind the cashier(收银台)in her general store.____ I quickly learned the importance of treating customers politely and saying “thank you.”

    At first I was paid in candy.____ I worked every day after school, and during the summer and on weekends and holidays from 8 a.m. to 7 p.m. My father helped me set up a bank account.____ 

    By the time I was 12, my grandmother thought I had done such a good job that she promoted me to selling cosmetics(化妆品). I developed the ability to look customers directly in the eye. Even though I was just a kid, women would ask me such things as “ What color do you think I should wear?” I took a real interest in their questions and was able to translate what they wanted into makeup(化妆)ideas.____

    The job taught me a valuable lesson: to be a successful salesperson, you didn't need to be a Rocket scientist—you needed to be a great listener.____ Except they are no longer women purchasing cosmetics from me; instead, they are kids who tell me which toys they would like to see designed and developed.

A. Later I received 50 cents an hour.

B. Before long, she let me sit there by myself.

C. I ended up selling a record amount of cosmetics.

D. Today I still carry that lesson with me: I listen to customers.

E. My grandma's trust taught me how to handle responsibility.

F. Soon I found myself looking more beautiful than ever before.

G. Watching my money grow was more rewarding than anything I could have bought.