问题 填空题

如图所示,把一块表面很干净的玻璃板挂在弹簧测力计下面,手持弹簧测力计上端,把玻璃板往下慢慢的放到刚好和一盆水的水面接触,再慢慢地提起弹簧测力计,则弹簧测力计的读数将________ (填“变大”“变小”或“不变”),这说明了______________.

答案

变大;分子间有引力

题目分析:当分子间距离小于分子直径的10倍时,物体的分子之间存在相互作用的引力和斥力,可以从分子间的作用力上来分析。由于玻璃和水接触在一起,使玻璃分子和水分子间的距离小于了分子直径的10倍;故向上提起弹簧测力计时,由于水分子和玻璃分子之间存在相互作用的引力,所以弹簧测力计的示数会大一些。

阅读理解

The geographical location of a country and its physical characteristics are very important to its development and progress. he United States is very fortunate in this respect.

First of all, it has a good climate. In almost all sections of the country it is possible to live comfortably during the whole year. It is true that in the south it sometimes gets very hot, and in the north very cold. But the people who live in these regions become accustomed to the climate and never suffer very much when the weather is either very hot or very cold.

In a large country there is usually a great variety of different physical characteristics. In the United States, there are wide plains and high mountains, thousands of lakes and rivets of all sizes, cool forests and hot deserts, and a coastline several thousand miles long.

The many lakes and rivers, as well as the long coastline, have been of great importance to the development of the country, since they made possible the easy transportation of people and all the things people need. Transportation by water is still necessary and important. In modern times, however, trains, automobiles, trucks and airplanes are doing much of the work which was formerly done by ships and boats.

44.What are the principal physical characteristics of the United States?

A.Almost the same.  B.Rather various.

C.Very good for farming. D.Suitable for transportation.

45.In what respect is the United States very fortunate?

A.Geographical location.  B.Good climate.

C.Physical characteristics.       D.Both A and C.

46.Why are rivers,lakes and coastlines important to the development of the U. S. A?

A.They make the climate better.

B.They provide people with a good many opportunities of employment.

C.They provide people with good transportation and whatever they need.

D.They make the scenery of the country more beautiful and attractive.

47.What was used for transportation in the distant past in the U. S. A. ?

A.Trains.   B.Trucks.

C.Planes.   D.Ships and boats.

单项选择题