问题 选择题

在万有引力的发现过程中,许多的物理学家做出了积极的贡献,其中最早在实验室中测量出引力常量的科学家是

A.牛顿

B.伽利略

C.卡文迪许

D.开普勒

答案

答案:C

题目分析:牛顿在推出万有引力定律的同时,并没能得出引力常量G的具体值.G的数值于1789年由卡文迪许利用他所发明的扭秤得出.卡文迪许的扭秤试验,不仅以实践证明了万有引力定律,同时也让此定律有了更广泛的使用价值.

牛顿在推出万有引力定律的同时,并没能得出引力常量G的具体值.G的数值于1789年由卡文迪许利用他所发明的扭秤得出.故选C.

点评:卡文迪许测出的G=6.7×10-11 Nm2/kg2,与现在的公认值6.67×10-11Nm2/kg2 极为接近;直到1969年G的测量精度还保持在卡文迪许的水平上.

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完形填空

对话填空(共10小题,每小题1分,满分10分)

Jack-J; Laura-L

J: I’d like to mail this box to Hong Kong. How much will it be, please?

L: Do you want to send it first class or second class?

J: How much is first class and how (76)l      does it take?                               小题1:  

L: It’s a light box. First class would cost $ 8.20. I(77)g     it                                  小题2:    

will take about eight to ten days to arrive.

J: And second class?

L: Sending it second class would be (78) c      ,                                             小题3:    

but it wouldn’t arrive (79)u     about a month from now. You’ll pay $ 4.90 only.小题4: 

J: Oh, I want it to arrive (80)e     than that. I’ll mail it first class.                           小题5:    

L: What’s in the box? I need to know in order to(81) c      the form.               小题6:    

J:A(82)s       of glasses.                                            小题7:   

Are there any other forms I need to fill out because it’s going to a foreign country?

L: Yes , one more. You have to write clearly what is in the box and the (83) v      小题8:

J: Here it is.

L: You forgot to put a return address on this box. It’s not a post office rule,

but we usually (84)a   people that all mail have a proper return address.                小题9:

J: OK. I’ll do it right now. I’ll also buy ten 60-cent stamps.

L: Let’s see. The box and the stamps. Your (85)t      bill comes to $ 14.20.       小题10:  

J: Thank you.