问题 实验题

在《探究小车速度变化规律》实验中,得到如图所示的一条纸带。已知打点计时器打点的时间间隔为0.02s,纸带上的各个点均为计数点(相邻两个计数点之间还有四个点图中未画出)。测量数据及其标记符号如图所示。

(1)打点计时器打下第4个点时小车的速度大小为       m/s。(保留三位有效数字)

(2)该同学用两种方法处理数据,并求出小车的加速度(T为相邻两计数点的时间间隔):

方法A:由……,取平均值求出加速度a。

方法B:由取平均值求出加速度a。

从数据处理方法看,在X1、X2、X3、X4、X5、X6中,对实验结果起作用的,方法A中有_______;方法B中有_____     (填写字母)。因此,选择方法___________(填AB)更合理,求得小车的加速度大小是         ____m/s2(保留三位有效数字)。

答案

1.47 、  X1   X6   、X1   X2  X3   X4   X5   X 、  B 、  3.12

单项选择题
单项选择题

During the last thirty years, the international economy has experienced a basic change. Improvements in the Internet and other communications have had important effects on world markets. Faster methods of transport from one place to another have made the world seem smaller to the businessmen. As a result, the world no longer consists of a number of separate economies under the control of different nations. Instead, the nations have been integrated into a single economy, and the integration is becoming more and more complete every year. For the first time in history, we can truly speak of a global economy.

The most dramatic example of this integration was the oil crisis of 1973 and 1974. It came as a great surprise to the public in the industrial nations to discover that they depended so heavily on imported oil. However, the best evidence for the growing integration is the rapid expansion in the volume of world trade. It went up by about 7% a year during the decade from 1990 to 2000, and in several quasi-industrial (半工业的) countries the growth was even more rapid. As a result. some imported products have become as common as domestic commodity. Some of them are too common for the public to any more realize they are foreign.

Production has also become international, which is manifested by the large corporations stepping across national borders and established branches and subsidiaries in several different countries. As an example, U. S. companies are building automobiles in Canada. Germany, Britain and Japan. In some cases, components of an automobile are produced abroad and shipped to the United States, where it is then finished with the imported parts. When even the United States has the largest number of such corporations, it is not the only. Other multinationals, for instance, are based in Japan, France, Germany, the UK and Italy.

Labor, too, is much more mobile than in the past. Both skilled and unskilled workers can now readily migrate from one country to another. In Europe, for example, there are large numbers of Turkish workers employed in the Germany Economy. Doctors, lawyers, and other professionals are also finding it easier to work in foreign countries. The labor market has become international, and the number of expatriate workers is continuing to grow.

People in industrial nations felt greatly surprised by the oil crisis in 1973 and 1974 because ()。

A. they didn’t expect the crisis to occur so soon

B. they couldn’t live without oil

C. they found they were so dependent on foreign countries

D. they realized they were not the per nations at all