搜题请搜索小程序“爱下问搜题”
问题 问答题

有两个完全相同的瓶子，一个装满水后质量为320g，一个装满酒精（ρ酒精=0.8×103kg/m3）后质量是280g，求：瓶子质量是多少g？瓶子容积是多少cm3？

答案

设空瓶的质量为m瓶，则瓶子的容积可表示为V=

m总水-m瓶
ρ水
，同时还可表示为V=
m总酒-m瓶
ρ水
，

二者相等，即

m总水-m瓶
ρ水
=
m总酒-m瓶
ρ水
，

解这个等式得瓶子的质量m瓶=120g；

则瓶子的容积V=V水=V=

m总水-m瓶
ρ水
=
320g-120g
1g/cm3
=200cm3．

答：瓶子质量是多少120g；瓶子容积是200cm3．

单项选择题

从法律角度定义，合同实质上是一种( )。

A．协议

B．主张

C．要约

D．承诺
查看答案
填空题


In the following passage, there are 20 blanks representing the words that are missing from the context. You are to put back in each of the blanks the missing word． The time for this section is 20 minutes.
Where do you really come from And how did you get (1) where you live today DNA studies suggest that all humans today (2) from a group of African ancestors who—about 60,000 years ago— (3) a remarkable journey.
The Genographic Project is seeking to chart new (4) about the migratory history of the human species by (5) sophisticated laboratory and computer analysis of DNA contributed by hundreds of (6) of people from around the world． In this unprecedented and real-time (7) effort, the Genographic Project is closing the gaps of what science (8) today about mankind’s ancient migration stories.
The Genographic Project is a five-year (9) partnership led by National Geographic Explorer-in-Residence Dr. Spencer Wells. Dr. (10) and a team of renowned international scientists and IBM researchers, are (11) cutting-edge genetic and computational technologies to analyze historical patterns in DNA (12) participants around the world to better understand our human genetic roots. (13) three components of the project are: to gather field research data (14) collaboration with indigenous and traditional peoples around the world; to invite (15) general public to join the project by purchasing a Genographic Project Public Participation Kit; (16) to use proceeds from Genographic Public Participation Kit sales to further (17) research and the Genographic Legacy Fund which in (18) supports indigenous conservation and revitalization projects. The Project is anonymous, non-medical, (19) , non-profit and non-commercial and all results will be placed in the (20) domain following scientific peer publication.

查看答案