问题 选择题

如图所示的是一种叫做蹦极的游戏。游戏者将一根有弹性的绳子一端系在身上,另一端固定在高处,从高处跳下。图中a点是弹性绳自然下垂时绳下端的位置,c点是他所到达的最低点的位置。对于他离开跳台至最低点的过程,下面说法正确的是:

A.他的重力势能一直在减小

B.绳的弹性势能一直在减小

C.他的动能在前一段时间在减小,后一段时间在增加

D.在最低点,重力势能减到最小,动能为零,绳的弹性势能最小

答案

答案:A

A.正确

B.绳的弹性势能一直在增大

C.他的动能在前一段时间在增加,后一段时间在减少

D.在最低点,重力势能减到最大,动能为零,绳的弹性势能最大

故选A

选择题
单项选择题

Emotion is a feeling about or reaction to certain important events or thoughts. People enjoy feeling such pleasant emotions as love, happiness, and contentment. They often try to avoid feeling unpleasant emotions, such as loneliness, worry, and grief.
Individuals communicate most of their emotions by means of words, a variety of sounds, facial expressions, and gestures. For example, anger causes many people to frown, make a fist, and yell. People learn ways of showing some of their emotions from members of their society, though heredity (遗传)may determine some emotional behavior. Research has shown that different isolated peoples show emotions by means of similar facial expressions.
Charles Darwin, famous for the theory of natural selection, also studied emotion. Darwin said in 1872 that emotional behavior originally served both as an aid to survival and as a method of communicating intentions. According to the James-Lange theory of emotions developed in the 1880s, people feel emotions only if aware of their own internal physical reactions to events, such as increased heart rate or blood pressure. But this theory was not up-held: by research on cats that had their nervous system damaged. The cats could not feel their body’s internal changes, but they showed normal emotional behavior. John B. Watson, an American psychologist who helped found the school of psychology called behaviorism, observed that babies stimulated by certain events showed three basic emotions--fear, anger, and love. Watson’s view has been challenged frequently since he proposed it in 1919.
The most widely accepted view is that emotions occur as a complex sequence of events. The sequence begins when a person encounters an important event or thought. The person’s interpretation of the encounter determines the feeling that is likely to follow. For example, someone who encounters a bear in the woods would probably interpret the event as dangerous. The sense of danger would cause the individual to feel fear. Each feeling is followed by physical changes and desires to take action, which are responses to the event that started the sequence. Thus, a person who met a bear would probably run away.
Several American psychologists independently developed the theory that there are eight basic emotions. These emotions--which can exist at various levels of intensity--are anger, fear, joy, sadness, acceptance, disgust,
surprise, and interest or curiosity. They combine to form all other emotions, just as certain basic colors produce all others.

In the sequence of events for emotions to occur, which is next to the encounter of an important event

A. Interpretation made.
B. Responses produced.
C. Feeling stimulated.
D. Action taken.