问题 选择题

不计空气的作用,小球沿固定光滑斜面下滑的过程中受到的作用力共有(  )

A.一个

B.两个

C.三个 

D.四个

答案

答案:B

地球表面的一切物体都受到重力;物体与斜面之间相互挤压,故一定受到支持力;

光滑表示没有摩擦力;故物体只受重力和支持力,两个力;

受力分析是解决力学题的基础,可以按照重力、弹力、摩擦力的顺序分析,最后要画出受力图.

单项选择题

In ancient Greek, the term euthanatos meant "easy death". Today euthanasia (安乐死) generally refers to mercy killing, the voluntary (自愿) ending of the life of someone who is terminally ill. Like abortion, euthanasia has become a legal, medical, and moral issue over which opinion is divided.

Euthanasia can be either active or passive. Active euthanasia means that a physician or other medical personnel takes an action that will result in death, such as giving an overdose of deadly medicine. Passive euthanasia means letting a patient die for lack of treatment, or stopping the treatment that has begun. Examples of passive euthanasia include taking patients off a breathing machine or removing other life-support systems. Stopping the food supply is also considered passive.

A good deal of the debate about mercy killing originates from the decision-making process. Who decides whether a patient is to die This issue has not been solved legally in the United States. The matter is left to state law, which usually allows the physician in charge to suggest the option of death to a patient’s relatives, especially if the patient is brain dead. In an attempt to make decisions about when their own lives should end, several terminally ill patients in the early 1990s used a controversial suicide device, developed by Dr. Jack Kevorkian, to end their lives.In parts of Europe, the decision-making process has become very flexible. Even in cases where the patients are not brain dead, patients have been put to death without their approval at the request of relatives or at the suggestion of physicians. Many cases of passive euthanasia involve old people or newborn infants. The principle justifying this practice is that such individuals have a "life not worthy of life".In countries where passive euthanasia is not legal, the court systems have proved very tolerant in dealing with medical personnel who practice it. In Japan, for example, if physicians follow certain guidelines they may actively carry out mercy killings on hopelessly ill people. Courts have also been somewhat tolerant of friends or relatives who have assisted terminally ill patients to die.

A terminally ill patient is one who ().

A. gets worse every day

B. can never get well again

C. is very seriously ill in the end

D. is too ill to want to live on

多项选择题