问题 解答题

一个直角三角形,两条直角边分别是6厘米和10厘米,沿斜边旋转一周后,得到一个旋转体,求旋转体的体积是多少?

答案

如图:

AB=6,BC=10,AC=2

34
,OB=
15
34
17

V=

1
3
×π×OB2×AC,

=

1
3
×3.14×
15
34
17
×
15
34
17
×2
34

=

942
34
17
(立方厘米);

答:旋转体的体积是

942
34
17
立方厘米.

阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两处为多余选项。

  1   First, the radioactive material must travel from its place of production to the power station. Although the power stations themselves are strongly built’, the .containers used for the transport of the materials are not. 2 Unfortunately, both’ of these may have an effect on the general public, since they are sure to pass near, or even through heavily populated areas.

Second, there is the problem of waste.  3  It is impossible to make these wastes non—radioactive, and so they must be stored in one of the inconvenient ways .that scientists have invented.For example? they may be buried under the ground, or dropped into deserted mines, or sunk in the sea.However, these methods do not ’solve the problem, since an earthquake could easily break the containers.

Third, there may occur the danger of a leak or an explosion at the power station.As with the other two dangers, this is not very likely to take place. However, it can happen.

Separately, these three types of dangers are not a great cause for worry.  5 

A.It is unusual for radioactive materials to be transported across land.

B.There are three separate sources of danger in supplying energy by nuclear power.

C.All nuclear power stations produce wastes that in most cases will remain radioactive for thousands of years.

D.The general public are strongly against the nuclear program. E.So it does not provide a serious objection to the nuclear program.

F.Normally, only two methods of transport are in use, namely road or rail.

G.But when they are taken together, the probability of disaster is extremely high.

单项选择题