问题 选择题

如图1为粗糙轨道,小球以大小为v0的初速度由A端向右运动,到B端时的速度大小为vB(A、B两端在同一水平面上);若以同样大小为v0的初速度由B端向左运动,到A端时的速度大小为vA。已知小球运动过程中始终未离开该粗糙轨道。下列说法正确的是(    )

A.vA>vB         B.vA=vB    

C.vA<vB         D.两个过程中小球机械能均守恒           

答案

答案:A

因为速度大时,对地面的压力大,则摩擦力大,故动能减小较大,比较两次情况,由A端向右运动比由B端向左运动,动能损失的较大,故A正确。

单项选择题
单项选择题

Social control refers to social processes, planned or unplanned, by which people are taught, persuaded, or forced to conform to norms. In every society, some punishments or negative sanctions are established for deviant behavior. Without deviant behavior there would not be need for social control and without social control there would not be a way of recognizing the boundary between the acceptable and the unacceptable.

Social control may be either formal or informal. Informal mechanisms include expressions of disapproval by significant others and withholding of positive rewards for disapproved behavior. Most people internalize norms in the course of socialization. This is any group’s most powerful protection against deviance, in that the individual’s own conscience operates as an agent of social control. When informal sanctions fail, formal agents of social control may be called upon. In contemporary society, such formal agents and agencies include psychiatry and other mental health professions; mental hospitals; police and courts of law; prisons; and social welfare agencies. All these formal agents function to limit, correct, and control violation of norms. Conflict theorists would also point out that social control agents and systems tend, in any society, to serve the interests of powerful groups and to enforce the norms most beneficial to those who make the rules and who, therefore, define unacceptable behavior.

Social control, whether formal or informal, has a dual function. First, it punishes the wrongdoer and reaff’irms the boundaries of acceptable behavior. Second, and less recognized, it regulates the manner in which deviants are treated.

In the third paragraph, "a dual function" refers to ().

A. formal and informal

B. rewards and penalties

C. approval and disapproval

D. clarification and regulation