问题 多选题

如图所示,ABCD为匀强电场中相邻的四个等势面,一个电子垂直经过等势面D时动能为20eV,经过等势面C时的电势能为-10eV,到达等势面B时速度恰好为零,已知相邻等势面间距离为5cm,则下列说法正确的是(  )

A.A等势面的电势为-10V

B.匀强电场的场强为200V/m

C.电子再次经过D等势面时,动能为l0eV

D.电子的运动是匀变速直线运动

答案

A、电子从B到D过程,根据动能定理得:-eUDB=0-EkD,解得,UDB=20V,由于是等差的等势面,则知,A等势面的电势为-10V.故A正确.

B、对于BD段:电场强度为E=

UDB
d
=
20
10×10-2
=200V/m.故B正确.

C、根据能量守恒可知,电子再次经过D等势面时,电势能不变,动能不变,其动能仍为20eV;故C错误.

D、根据电场线与等势面垂直可知,该电场是匀强电场,电子做匀变速直线运动.故D正确.

故选ABD

判断题
阅读理解

Welcome to enj oy the Mattaponi powwow(meeting oi North America Indians)and culture day!

Created in Virginia,America,the Mattaponi Indian Museum sits on a cliff(悬崖)overlooking the Mattaponi River.The Matta—ponis have worked hard to keep their ancient way of life,customs and ceremonies. One purpose of their yearly powwow is to share these traditions with you.

MATTAPONI POWWOW AND CULTURE DAY:May 18

ADMISSION:Adult—$6.00  Children(under 12)—Free

Come and spend the day with us on the shores of the Mattaponi River for an educational experience presenting the customs and beliefs of the Mattaponi.During this special day,American Indians will dance and play drums while dressed in tribal clothing.This year visitors may join in the dancing and trumming.Visitors will be able to observe artists and craftsmen(工匠)as they show their basket-making and tool-making skills.American storytellers will help you see how their habits and beliefs are passed on to their children through stories.

Enjoy Activities

●Taste American Indian foods

●Purchase crafts and souvenirs

●Play American Indian children’s games

●Watch ceremonial dances and listen to ceremonial songs

Important Cautions

●No pets

●Bring your own chairs and blankets

●Tickets may be purchased in advance although no refunds(退款)will be allowed

For more information,please visit http: //www.hemattaponireservation.com/main.

小题1:According to the text,the Mattaponis’habits and beliefs are handed down from generation to generation through      .

A.songs

B.stories

C.crafts

D.dance小题2:Visitors coming to enjoy the Mattaponi powwow and culture day can do all the following EXCEPT       

A.enjoy American Indian foods

B.watch ceremonlal dances

C.play American Indian children’s games

D.get crafts and souvenirs for free小题3:This text is mainly intended to       

A.inform readers about an event

B.persuade readers to try drumming

C.sell crafts and souvenirs to readers

D.educate readers on different types of powwows