问题 选择题

一个质量为1kg的物体在光滑水平面上A、B两点的正中间由静止开始运动(设不会超越A、B),其水平方向的外力F随时间的变化如图所示.设向A的外力F为正方向,若从出发开始计时,则物体的运动情况是(  )

A.在AB间作往返运动,4s末将处于原处

B.在AB间作往返运动,4s末将处于偏向A的某点

C.一直向A运动,4s末将处于偏向A的某点

D.一直向B运动,4s末将处于偏向B的某点

答案

由图分析可知,物体在第1s内向A做匀加速运动;第2s内,物体继续向A做匀减速运动,2s末速度减为零;第3s内,物体向A做匀加速运动;第4s内,物体向A做匀减速运动;所以物体一直向A运动.由于加速度大小保持不变,相邻加速与减速时间相等,根据对称性可知,4s末物体的速度为零,处于偏向A处的某点.故C正确,ABD错误.

故选C.

完形填空

Our world is full of rules. Everyone needs to obey them. But      your idea about your school rules? Now many students like to talk about the rules that they have      . At their school, they      wear uniforms every day. The problem is that all the students think the uniforms are        . They think young people should look smart and so they would like to wear their own clothes.      , their teachers believe that if they did that, they would think       of their clothes than their study.       the students disagree. They would feel more comfortable and that is good for      . If they can’t do that, they        design their own uniforms. That would be a good way to      both teachers and students happy.

It’s also probably a good idea for parents to allow teenagers to study in groups during the evening.  Although they get        sometimes, they can learn a lot from each other. They also think that vacations should be longer. At present they’re too      . Longer vacations would give them time to do things like volunteering. On Friday afternoons, many students are sleepy after a long week of classes. They think it’s better to have Friday afternoons        to volunteer and help others.        , it is helpful for students to go to an old people’s home to sing and perform a play for them. It will help them understand the meaning of love. It’s also better to volunteer at the local hospital. It would be a good         for them because some of them want to be doctors when they grow up.

What do you think of your school rules?

小题1:

A.how’s

B.what’s

C.how’re

D.what’re小题2:

A.at home

B.in hospital

C.after class

D.in school小题3:

A.have to

B.may

C.can’t

D.mustn’t小题4:

A.comfortable

B.smart

C.ugly

D.nice小题5:

A.Although

B.However

C.Yet

D.Still小题6:

A.much

B.more

C.little

D.less小题7:

A.And

B.So

C.Or

D.But小题8:

A.studying

B.studies

C.health

D.healthy小题9:

A.should be allowed to

B.aren’t able to

C.aren’t allowed to

D.will have to小题10:

A.keeping

B.be

C.keep

D.being小题11:

A.quietly

B.quickly

C.happily

D.noisy小题12:

A.shorter

B.longer

C.long

D.short小题13:

A.off

B.of

C.on

D.down小题14:

A.For example

B.By the way

C.To be honest

D.Such as小题15:

A.teacher

B.experience

C.doctor

D.rule

问答题 简答题