半径为R的光滑半球固定在水平面上，现用一个方向与球面始终相切_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

半径为R的光滑半球固定在水平面上，现用一个方向与球面始终相切的拉力F把质量为m的小物体（可看做质点）沿球面从A点缓慢地移动到最高点B，在此过程中，拉力做的功为

A．πFR

B．πmgR

C．mgR

D．mgR

答案

答案：D

题目分析：小物体在缓慢（匀速）运动过程中，只有重力和F做功，根据动能定理：W_拉－mgR=ΔE_k＝0，则拉力做功W_拉＝mgR，D正确。

单项选择题

茵陈蒿汤的配伍体现了下列何项（）。

A.利湿与泄热相伍

B.化湿与温阳相配

C.燥湿与祛瘀同用

D.祛湿与行气配伍

E.利湿与养阴合用

补全对话，情景问答

补全对话，从方框中选择最佳选项完成对话，有两项多余。

A. won't you?
B. don't you?
C. go with us.
D. But I'd like to stay at home.
E. Where do you think we should go?
F. And you got ready for it,
G. you needn't tell your parents.

A:A lovely day, isn't it? We can go out to play.
B: Yes.   1
A: That will be a pity if you only stay at home in such fine weather.
B:   2
A: What about going to the East Lake this afternoon? It's a great place for fun.
B:  3    didn't you?
A: It's true. We have invited four friends to go there. If you like,   4
B: Er, I'd better ask my mother first, OK?
A: Sure. We' ll wait for you till 12 at noon. Please call me if you go,   5
B: OK. Thanks! I will.
1._______2.________3.______4._______5.________