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问题 选择题

竖直平面内光滑圆轨道外侧，一小球以某一水平速度v0从A点出发沿圆轨道运动，至B点时脱离轨道，最终落在水平面上的C点，不计空气阻力．下列说法中不正确的是（　　）

A．在B点时，小球对圆轨道的压力为零

B．B到C过程，小球做匀变速运动

C．在A点时，小球对圆轨道压力大于其重力

D．A到B过程，小球水平方向的加速度先增加后减小

答案

A、小球在B点恰好脱离轨道，则小球与轨道间恰好无相互作用力，故A正确

B、从B到C过程，小球只受重力作用，做匀变速曲线运动，故B正确

C、在A点，小球具有竖直向下的向心加速度，此瞬间处于失重状态，对轨道的压力小于其重力，故C错误

D、小球在A点时合力沿竖直方向，在B点时合力也沿竖直方向，但在中间过程某点支持力却有水平向右的分力，所以小球水平方向的加速度必定先增加后减小，故D正确

本题选不正确的，故选C

阅读理解
B
HIGHFIELD COMPREHENSIVE SCHOOL
SCHOOL REPORT
Form Teacher: G. Baker            Pupil’s Name:  Simon Watkins
Term:        Summer 2010            Form:        Ⅳ B
Subject
Exam
Class work
Comments
English
59
61
Simon has reached a satisfactory standard but now needs to apply himself with more determination.
Mathematics
77
85
Sound work and progress throughout the year. Well done!
History
46
53
A disappointing exam result. He is unable to give attention to this subject for long.
Chemistry
78
85
His obvious ability in the subject was not fully reflected in his exam work, but I have high hopes for him nevertheless.
Physics
86
94
An excellent term’s performance. He goes from strength to strength. A born scientist, I feel.
Biology
57
60
This time next year he will be taking the “0” exam. He needs to concentrate on the work, not on class conversation.
French
41
46
Clearly he didn’t bother to revise. His general attitude is far too casual.
Physical
Education
/
31
Weak. It’s time he exercised his body more and his voice less. He should try to work with a team.
FORM TEACHER’S REMARKS                                       HEADMASTER
Basically satisfactory work and progress               I shall be keeping an eye on his
though he will now have realized, I hope, that          progress in his weaker subjects
in certain subject areas he needs to make speedy     though his success in the
improvement.                               science is most pleasing.
小题1:According to the comments of the Physical Education teacher, Simon _____.
A．is too talkative in the class
B．likes to work with his classmates
C．doesn’t exercise his body at the right time
D．becomes weak because he doesn’t exercise at all
小题2: Which of Simon’s subjects will attract the headmaster’s attention in future?
A．Biology and Maths.B．History and French.
C．English and Chemistry.D．Physics and Physical Education.
小题3:Which of the following statements best describes Simon?
A．He has made great progress in language classes.
B．His potential has been fully reflected in science classes.
C．His grade in maths makes him a born scientist.
D．He needs to improve his attitude on certain subjects.
小题4:Based on the school report, which of the following statements is true?
A．Simon didn’t bother his teacher to revise French.
B．Basically, Simon did a good job in science.
C．Simon is a determined learner in English.
D．Simon is able to pay attention to history for long.
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单项选择题

下列建筑是由赵安中先生捐建的是（）

①宁大教工生活小区“杏琴园”

②老行政楼

③“林杏琴会堂”

④宁大幼儿园

A.①③

B.①④

C.①③④

D.①②③④
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