问题 实验题

在“验证机械能守恒定律”的实验中,打点计时器接在电压为U,频率为f的交流电源上,在实验中打下一条理想纸带,如图所示,选取纸带上打出的连续5个点A,B,C,D,E,测出A点距起始点O的距离为x0,点A,C间的距离为x1,点C,E间的距离为x2,已知重锤的质量为m,当地的重力加速度为g,则

(1)从起始点O到打下C点的过程中,重锤重力势能的减少量△Ep=____,重锤动能的增加量△Ek=___。

(2)根据题中提供的条件,还可求出重锤实际下落的加速度a=_____。

答案

(1)mg(x0+x1),

(2)

完形填空

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Starting high school means changes in your life.Most teenagers look forward to the first day of high school, but still feel a little bit nervous.In order to make your high school life easier, ____小题1:____

Learn all you can about your first day before the first school day.Take part in some activities that are held at the school for new students to know the school better.If parents are invited to these activities, take yours with you.Carefully look over all the materials you receive.____小题2:____

Get the things you will need for class.Buy the things suggested on your teachers’ supply lists and place your materials for each class separately.

____小题3:____ If you find you’re not doing well in a subject, make use of after-school study groups or ask your teacher to help you with your schoolwork.Consider private tutoring to get you through a difficult time.

There’s more extracurricular (课外的) activities in high school than in middle school, such as clubs, music and theatre groups, student government, and sports teams.Make friends and be seen at such school activities.____小题4:___ Ask someone in the school office about opportunities to take part in school activities if you don’t know how.This is a good time to do what you like doing and an opportunity to try new things.Who said school has to be all work and no play?

Since you’re attending more activities in high school than in middle school, ____小题5:____

A.you can follow these tips.

B.Keep up with your high school workload.

C.here are some tips for you to follow.

D.Be sure you know where the school’s buildings are.E.you’ll have to learn to manage your time.

F.Join a club or other organizations to meet people and develop friendships.

G.All work and no play makes Jack a dull boy.

单项选择题