问题 选择题

水平抛出在空中飞行的物体,不考虑空气阻力,则下列说法不正确的是(  )

A.在相等的时间间隔内动量的变化相同

B.在任何时间内,动量变化的方向都是竖直方向

C.在任何对间内,动量对时间的变化率恒定

D.在刚抛出物体的瞬间,动量对时间的变化率为零

答案

A、根据动量定理,动量的变化△P=Gt,G恒定不变,在相等的时间间隔内动量的变化△P相同.故A正确.

    B、根据动量定理:平抛物体动量变化的方向与重力方向相同,不变.故B正确.

    C、D由动量定理变形得

△P
t
=G,平抛物体动量对时间的变化率恒定.故C正确,D错误.

本题选不正确的,故选D.

单项选择题
阅读理解

Attitude is an internal state that influences the choices of personal action made by the individual. Some researchers consider that attitudes come from differences between beliefs and ideas; others believe that attitudes come from emotional states. Here, we focus on the effects of attitudes upon behavior, that is, upon the choices of action made by the individual.

The kinds of actions taken by human beings are obviously influenced greatly by attitudes. Whether one listens to classical music or rock, whether one obeys the speed limit while driving, whether one encourages one’s husband or wife to express his or her own ideas—all are influenced by attitudes. These internal states are acquired throughout life from situations one is faced with in the home, in the streets, and in the school.

Of course, the course of action chosen by an individual in any situation will be largely determined by the particulars of that situation. An individual who has a strong attitude of obeying laws may drive too fast when he is in a hurry and no police cars in sight. A child who has a strong attitude of honesty may steal a penny when she thinks no one will notice. But the internal state which remains unchanged over a period of time, and which makes the individual behave regularly in a variety of situations, is what is meant by an attitude.

Attitudes are learned in a variety of ways. They can result from single incidents, as when an attitude toward snakes is acquired by an experience in childhood at the sudden movement of a snake. They can result from the individual’s experiences of success and pleasure, as when someone acquires a positive attitude toward doing crossword puzzles by being able to complete some of them. And frequently, they are learned by copying other people’s behavior, as when a child learns how to behave toward foreigners by observing the actions of his parents. Regardless of these differences, there is something in common in the learning and modification(修正)of attitudes.

小题1: According to the passage, attitudes _________.

A.come from different situations in one’s life

B.are largely affected by one’s behavior

C.remain unchanged in one’s daily life

D.could be chosen according to one’s will小题2:The author uses the examples in Paragraph 3 to show _________.

A.people often make mistakes when they are not noticed

B.people with good attitudes may sometimes do bad deeds

C.particulars of a situation may influence an individual’s action

D.an individual may change his or her attitude fairly easily小题3:Which of the following is TRUE about the learning of attitudes?

A.Attitudes are only learned through one’s success.

B.Attitudes learned in danger will last longer.

C.Copying others behavior is not a good idea.

D.Attitudes can be learned from one’s parents.小题4:What would be the best title for the passage?

A.Differences of Attitudes.

B.Nature of Attitude.

C.Choices of Attitudes.

D.Modification of Attitude.