已知地球半径为R，质量为M，自转角速度为（ ，万有引力恒量为G，地球同步卫星距地面高度为h，则（ ）
A．地面赤道上物体随地球自转运动的线速度为（R
B．地球同步卫星的运行速度为（h
C．地球近地卫星做匀速圆周运动的线速度为
D．地球近地卫星做匀速圆周运动的周期大于
AC
题目分析：地面赤道上物体随地球自转的角速度等于地球自转的加速度，半径等于地球半径R，根据
可求地面赤道上物体随地球自转运动的线速度为（R，所以A正确；地球同步卫星的轨道半径为R+h，所以其线速度为
，所以B错误；地球近地卫星的线速度，根据
可求
，所以C正确；
，得，所以地球近地卫星的角速度大于同步卫星的角速度，故也大于地球自转的角速度，再根据
可知，地球近地卫星做匀速圆周运动的周期小于
，所以D错误。
| Cooperation is the common endeavor of two or more people to perform a task or reach a jointly cherished goal. Like competition and conflict, there are different forms of cooperation, based on group organization and attitudes. In the first form, known as primary cooperation, group and individual unite. The group contains nearly all of each individual’s life. The rewards of the group’s work are shared with each member. There is an interlocking identity of individual, group, and task performed. Means and goals become one, for cooperation itself is valued. While primary cooperation is most often characteristic of preliterate societies, secondary cooperation is characteristic of many modem societies. In secondary cooperation, individuals devote only part of their lives to the group. Cooperation itself is not a value. Most members of the group feel loyalty, but the welfare of the group is not the first consideration. Members perform tasks so that they can separately enjoy the fruits of their cooperation in the form of salary, prestige, or power. Business offices and professional athletic teams are examples of secondary cooperation. In the third type, called tertiary cooperation or accommodation, latent conflict underlies the shared work. The attitudes of the cooperating parties are purely opportunistic; the organization is loose and fragile. Accommodation involves common means to achieve antagonistic goals; it breaks down when the common means cease to aid each party in reaching its goals. This is not, strictly speaking, cooperation at all, and hence the somewhat contradictory term antagonistic cooperation is sometimes used for this relationship. |
What is the author’s main purpose in Paragraph 1 of the passage
A．To explain how cooperation differs from competition and conflict
B．To show the importance of group organization and attitudes
C．To offer a brief definition of cooperation
D．To urge readers to cooperate more often