问题 填空题

三峡大坝水库水面下100m深处水的压强是______帕.大坝边上修筑的船闸是利用______原理工作的,开闸放水时,如果水位每下降1m,那么水对坝底每平方米面积减少的压力是______牛.

答案

水面下100m深处水的压强:

p=ρgh=1.0×103kg/m3×9.8N/kg×100m=9.8×105Pa;

人们根据连通器的原理修建了三峡大坝船闸,三峡大坝的船闸是世界上最大的连通器;

水位每下降1m,水对坝底减小的压强:

△p=ρg△h=1.0×103kg/m3×9.8N/kg×1m=9.8×103Pa;

水对坝底减小的压力:

△F=△pS=9.8×103Pa×1m2=9.8×103N.

故答案为:9.8×105;连通器;9.8×103

阅读理解

阅读理解。

     What makes a person a scientist? Does he have ways or tools of learning that are different from those

of others?

     The answer is"no". It isn't the tools a scientist uses but how he uses these tools that makes him a

scientist. You will probably agree that knowing how to use a power is important to a carpenter(木匠).

You will probably agree,too,that knowing how to investigate(调查) ,how to discover information,is

important to everyone. The scientist,however,goes one step further;he must be sure that he has a

reasonable answer to his questions and that his answer he gets to many questions is into a large set of

ideas about how the world works.

     The scientist's knowledge must be exact. There's no room for half right or right just half the time.  He

must be as nearly right as the conditions permit. What works under one set of conditions at one time must work under the same conditions at other times.  If the conditions are different,any changes the scientist

observes in a demonstration(实证) must be explained by the changes in the conditions. This is one reason why investigations are important in science. Albert Einstein,who developed the Theory of Relativity,

amved at this theory through mathematics. The accuracy (正确性) of his mathematics was later tested

through investigation.  Einstein's ideas were proved to be correct.  A scientist uses many tools for

measurements.  Then the measurements are used to make mathematical calculations (计算) that may test

his investigations.

1. What makes a scientist according to the passage?

A. The tools he uses.                            

B. His ways of learning.

C. The way he uses his tools.                      

D. The various tools he uses.

2."…knowing how to investigate,how to discover information,is important to everyone.

    "The writer says this toshow

A.  the importance of information

B. the difference between scientists and ordinary people

C.  the importance of thinking

D. the difference between carpenters and ordinary people

3. A sound scientific.theory should be one that _________.

A. works under one set of conditions at one time and also works under the same conditions at other times

B. doesn't allow any change even under different conditions

C. can only work under one condition

D. can be used for many purposes

4.  What is the main idea of the passage?

A. Scientists are different from ordinary people.

B.  The Theory of Relativity.

C.  Exactness is the core(核心) of science.      

D.  Exactness and way of using tools are the keys to making of a scientist.

不定项选择