问题 多选题

如图所示,a为放在赤道上相对地球静止的物体,随地球自转做匀速圆周运动,b为沿地球表面附近做匀速圆周运动的人造卫星(轨道半径等于地球半径),c

为地球的同步卫星,以下关于a、b、c的说法中正确的是(  )

A.a、b、c做匀速圆周运动的向心加速度大小关系为ab>ac>aa

B.b与c相比,b的发射速度大,运行速度vb

C.a、b、c做匀速圆周运动的线速度大小关系为va=vb>vc

D.a、b、c做匀速圆周运动的周期关系为Ta=Tc>Tb

答案

A、a与同步卫星c转动周期相等,根据a=ω2r=

2r
T2
,由于a的轨道半径小于同步卫星c的轨道半径,故a的轨道加速度小于同步卫星c的加速度,即ac>aa,而b的半径比c小,所以ab>ac,故A正确;

B、a与同步卫星c转动周期相等,根据v=

2πr
T
,由于a的轨道半径小于同步卫星c的轨道半径,故Va<Vc;根据卫星的线速度公式v=
GM
r
,由于人造卫星的轨道半径小于同步卫星的轨道半径,所以Vc<Vb;故va<vc<vb,发射卫星时,离地面越远,发射速度越大,所以b与c相比,b的发射速度大,故B正确,C错误;

D、根据卫星的周期公式T=

2πr
v
=
r3
GM
,由于近地卫星b的轨道半径小于同步卫星c的轨道半径,所以Tc>Tb,而Ta=Tc,所以Ta=Tc>Tb,故D正确.

故选ABD

单项选择题
阅读理解

Ammie Reddick from East Kilbride, Lanarkshire, was only 18 months old when she had the accident that had scarred(留下创伤) her for life. The curious child reached up to grab the wire of a hot kettle in the family kitchen and poured boiling water over her tiny infant frame.

Her mother Ruby turned round and, seeing Ammie horribly burnt, called an ambulance which rushed her daughter to a nearby hospital. Twenty percent of Ammie’s body had been burned and all of her burns were third-degree. There, using tissue taken from unburned areas of Ammie’s body, doctors performed complex skin transplants to close her wounds and control her injuries, an operation that took about six hours. Over the next 16 years, Ammie underwent 12 more operations to repair her body.

When she started school at Maxwelton Primary at age 4, other pupils made cruel comments or simply wouldn’t play with her. “I was the only burned child in the street, the class and the school,” she recalled, “some children refused to become friends because of that.”

Today, aged 17, Ammie can only ever remember being a burned person with scars; pain is a permanent part of her body. She still has to have two further skin transplants. Yet she is a confident, outgoing teenager who offers inspiration and hope to other young burns victims.

She is a member of the Scottish Burned Children’s Club, a charity set up last year. This month, Ammie will be joining the younger children at the Graffham Water Center in Cambridgeshire for the charity’s first summer camp. “I’ll show them how to get rid of unkind stares from others,” she says. Ammie loves wearing fashionable sleeveless tops, and she plans to show the youngsters at the summer camp that they can too. “I do not go to great lengths to hide my burns scars,” she says, “I gave up wondering how other people would react years ago.”

小题1:How many operations has Ammie already had?

A.Twelve

B.Thirteen

C.fourteen

D.Fifteen小题2:What did other children do when Ammie first went to school?

A.They were friendly to her.

B.They showed sympathy to her.

C.They were afraid of her.

D.They looked down upon her.小题3:Ammie will teach the younger children at the Graffham Water Center to___________.

A.face others’ unkindness bravely

B.hide their scars by proper dressing

C.live a normal life

D.recover quickly小题4:Which of the following words can’t properly describe Ammie?

A.Courageous

B.Confident

C.sensitive

D.Outgoing小题5:What can be the best title of the passage?

A.A Seriously Burned Girl Survives

B.Ways to Get Rid of Unkind Stares

C.Permanent Scars And Pain For a Girl

D.A seriously burned angel of Hope