如图所示,已知绳长为L1=20cm,水平杆L2=10cm,小球质量m=0.3kg

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问题:

如图所示,已知绳长为L1=20cm,水平杆L2=10cm,小球质量m=0.3kg,整个装置可绕竖直轴转动,重力加速度g=10m/s2,问:

(1)要使绳子与竖直方向成45°角,试求该装置必须以多大的角速度转动才行?

(2)此时绳子的张力?(结果可用根式表示)

考点:向心力
题型:问答题
情景交际。(15分)
(A)选择方框中的句子完成对话,其中有两项多余。(10分)
A:What’s the matter, Mrs. Smith?
B: 小题1:  I can’t do any work, doctor.
A:Do you have a cough?
B:No. I don’t have a cough.
A: 小题2: 
B:Yes, I sleep very well.
A:Do you have breakfast every morning?
B:No. I don’t have breakfast. And I have only a little food for lunch and supper because I want to keep thin.
A:Oh, I see.   小题3: You need to eat more food and have three meals a day.   小题4:
B:OK. I will do like that.
A: 小题5:
B:Thank you very much.
A.I feel very well.
B.I hope you will get better soon.
C.Do you sleep well at night?
D.I’m not feeling well.
E.And do some exercise every day.
F.You need to eat less food.
G.There is nothing serious.
题型:问答题

下列叙述正确的是(  )

A.汽油、柴油和植物油都是碳氢化合物

B.甲烷、乙烯和苯在工业上都可通过石油分馏得到

C.乙醇可以被氧化为乙酸,二者都能发生酯化反应

D.主链含5个碳原子的辛烷,其同分异构体最多只有5种

题型:问答题

管理部门对系统的要求是BSP设计的出发点,所以要确定管理部门对系统的要求,具体方法是______。

题型:问答题

依据GB/T18664-2002《呼吸防护用品的选择、使用与维护》,若空气污染物同时刺激眼睛或皮肤,应选择的防护面罩是()。

A.全面罩

B.半面罩

C.开放型面罩

D.送气头罩

题型:问答题

通常T-ALOS告警是由于()引起的。

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