问题 选择题

A、B、C三个物体运动的位移—时间图像如右图所示,则下列说法正确的是(    )

A.三个物体在10s内的位移相等

B.三个物体在10s内的平均速度相等

C.三个物体在10s内的平均速率相等

D.三个物体在10s内的路程相等

答案

AB

题目分析:位移表示由初位置指向末位置的有向线段,路程表示物体轨迹的长度,所以三者的路程不同,位移相同,从图中可知三者所用时间相同,平均速度等于位移和时间的比值,平均速率等于路程与时间的比值,所以三者的平均速度相同,平均速率不同,故AB正确,CD错误

故选AB

点评:本题很容易出错的是平均速度和平均速率的计算,关键是理解平均速度等于位移和时间的比值,平均速率等于路程与时间的比值,

阅读理解

A Municipal Report(Adapted from a story by O.Henry)(Ⅱ)

Azalea Adair herself opened the door when I knocked.She was about 50 years old.Her white hair was pulled back from her small,tired face.She wore a pale yellow dress.It was old,but very clean.

Azalea Adair led me into her living room.A damaged table,three chairs and an old red sofa were in the center of the floor.

Azalea Adair and I sat down at the table and began to talk.I told her about the magazine's offer an she told me about herself.She was from an old southern family.Her father had been a judge.

Azalea Adair told me she had never traveled or even attended school.Her parents taught her at home with private teachers.We finished our meeting.I promised to return with the agreement the next day, and rose to leave.

At that moment,someone knocked at the back door.Azalea Adair whispered a soft apology and went to answer the caller.She came back a minute later with bright eyes and pink cheeks.She looked ten year younger.“You must have a cup of tea before you go,”she said.She shook a little bell on the table,and small black girl about twelve years old ran into the room.

Azalea Adair opened a tiny old purse and took out a dollar bill.It had been fixed with a piece of blue paper and the upper right hand comer was missing.It was the dollar I had given to Uncle Caesar.“Go to Mr.Baker's store,Impy ,”she said,“and get me 25 cents' worth of tea and ten cents' worth of sugar cakes. And please hurry.”

The child ran out of the room.We heard the back door close.Then the girl screamed.Her cry mixed with a man's angry voice.Azalea Adair stood up.Her face showed no emotion as she left the room.I heard the man's rough voice and her gentle one.Then a door slammed and she came back into the room.“I am sorry,but I won't be able to offer you any tea after all,” she said.“It seems that Mr.Baker has no more tea.Perhaps he will find some for our visit tomorrow.”

We said good-bye.I went back to my hotel.

Just before dinner, Major Wentworth Caswell found me.It was impossible to avoid him.He insisted on buying me a drink and pulled two one-dollar bills from his pocket.Again I saw a torn dollar fixed with blue paper, with a corner missing.It was the one I gave Uncle Caesar.How strange,I thought. I wondered how Caswell got it.

63.We can judge from her behavior that Miss Adair was       

A.polite and elegant      B.confident and determined

C.poor and miserable    D.capable and hardworking

64.Adair seemed          after coming back from the back door.

A.as calm as before    B.sadder    C.excited    D.surprised

65.The angry man with a rough voice outside might be           .

A.Uncle Caesar    B.Mr.Baker    C.Caswell  D.A stranger

66.When the narrator saw Caswell again at his hotel,he was surprised         .

A.that Caswell should find him

B.that Caswell insisted on buying him a drink

C.that Caswell pulled two one-dollar bills from his pocket

D.to find Caswell had the torn dollar bill with a comer missing

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