问题 选择题

一水平的弹簧振子,以平衡位置O点为中心,在AB两点间作简谐振动,则(    )

A.振子在O点的速度和加速度都达到最大

B.振子的速度减小时,位移就增大

C.振子的加速度减小时,速度值一定变小

D.振子的速度方向与加速度方向可能相同,可能相反

答案

BD

此题涉及弹簧振子。在平衡位置,振子所受合外力为零,则加速度为零,故A选项错误。当远离平衡位置时,位移增大,回复力增大,加速度增大,速度减小。所以B选项正确,C选项错误。当远离平衡位置时,速度和加速度方向相反;靠 * * 衡位置时,相同。故D选项正确。本题考查了弹簧振子中的基本物理量,难度不大。

阅读理解

What should you think about in trying to find your career(职业)? You are probably better at some school subjects than others.  1 A boy who is good at mathematics can use that in an engineering career. 2 So it is important to do well at school. On the other hand, you may not have any specially strong or weak subjects but your records show a general satisfactory standard. 3 Knowledge of history is not required for most jobs but if history is one of your good subjects you will have learned to remember facts and details. This is an ability that can be useful in many jobs.

4 If nothing else, you may have learned how to get to work on time, to follow instructions and to get on with older workers. Just as important, you may become interested in a particular industry or career you see from the inside in a part-time job.

Facing your weak points is also part of knowing yourself. 5 Your school record, for instance, may not be too good, yet it is an important part of your background. You should not be apologetic about it but instead recognize that you will have a chance of a fresh start at work.

A.He may do well in his future work.

B.It is better to face any weaknesses than to pretend they do not exist.

C.Although not all subjects can be used directly in a job, they may have indirect value.

D.These may show strengths(优势) that you can use in your work.E. Your school must have taught you the skills.

F. A girl who spells well and likes English may be good at office work.

G. If you have had a part-time job on Saturday or in the summer, think what you gained from it.

单项选择题