问题 选择题

一个物体相对于另一个物体的位置改变叫做机械运动,它是绝对的,而静止是相对的,在有云的夜晚,我们抬头望月,觉得月亮在云中穿行,这时选取的参考系是(  )

A.月亮

B.地面

C.云

D.星

答案

参考系是研究运动时来当作参考的物体,是假定不动的.抬头望明月,觉得月亮在云中穿行,是月亮相对于云在运动,故参考系为云.选项ABD错误.C正确.

故选C.

填空题
单项选择题

At the company picnic, all of the employees who participated in more than four of the scheduled events, and only those employees, were eligible for the raffle held at the end of the day. Since only a small proportion of the employees were eligibly for the raffle, most of the employees must have participated in fewer than four of the scheduled events.
Which one of the following arguments exhibits a flawed pattern of reasoning most like that exhibited by the argument above

A.Only third-and fourth-year students are allowed to keep cars on campus. Since one quarter of the third-year students keep cars on campus and one half of the fourth-year students keep cars on campus, it must be that fewer third-year students than fourth-year students keep cars on campus.

B.Only those violin students who attended extra rehearsal sessions were eligible for selection as soloists. Since two of the violin students were selected as soloists, those two must have been the only violin students who attended the extra sessions.

C.The only students honored at a special banquet were the band members who made the dean’s list last semester. Since most the band members were honored, most of the band members must have made the dean’s list.

D.All of the members of the service club who volunteered at the hospital last summer were biology majors. Since ten of the club members are biology majors, those ten members must have volunteered at the hospital last summer.

E.(E) All of the swim team members who had decreased their racing times during the season were given awards that no other members were given. Since fewer than half the team members were given such awards, the racing times of more than half the team members must have increased during the season.