问题 计算题

(10分)一炮弹质量为m,相对水平方向以一定的倾角θ斜向上发射,发射速度为v,炮弹在最高点爆炸成两块,其中一块沿原轨道返回,质量为,求:

(1)另一块爆炸后瞬时的速度大小;

(2)爆炸过程系统增加的机械能。

答案

(1)3vcosθ      (2)2m(vcosθ)2

单项选择题 A1/A2型题
阅读理解

阅读理解

     It was Thanksgiving morning and in the crowded kitchen of my small home I was busy preparing the

traditional Thanksgiving turkey when the doorbell rang. I opened the front door and saw two small children in rags huddling together inside the storm door on the top step.

     "Any old papers, lady?" asked one of them.

     I was busy. I wanted to say "no" until I looked down at their feet. They were wearing thin little sandals, wet with heavy snow.

     "Come in and I'll make you a cup of hot cocoa."

     They walked over and sat down at the table. Their wet sandals left marks upon the floor. I served them cocoa and bread with jam to fight against the cold outside. Then I went back to the kitchen and started

again on my household budget.

     The silence in the front room struck me. I looked in. The girl held the empty cup in her hands, looking

at it. The boy asked in a flat voice, "Lady, are you rich?"

     I looked at my shabby slipcovers. The girl put her cup back in its saucer carefully and said, "Your cups match your saucers." Her voice was hungry with a need that no amount of food could supply. They left

after that, holding their bundles of papers against the wind. They hadn't said "Thank you." They didn't need to.They had reminded me that I had so much for which to be grateful. Plain blue china cups and saucers

were only worth five pence. But they matched.

     I tasted the potatoes and stirred the meat soup. Potatoes and brown meat soup, a roof over our heads, my man with a good steady job-these matched, too.

     I moved the chairs back from the fire and cleaned the living room. The muddy prints of small sandals

were still wet upon my floor. Let them be for a while, I thought, just in case I should begin to forget how

rich I am.

1. Two children came to the writer's front door because __________.

A. it was Thanksgiving Day    

B. they were beggars

C. they wanted old papers          

D. they wanted a cup of cocoa

2. Why did the writer let the children in?

A. She showed great pity on them.    

B. She had old papers to sell. 66~70 CABCD

C. She wanted to invite them to her Thanksgiving feast.

D. She wanted them to see how rich she was.

3. The girl thought the writer was rich perhaps because __________.

A. she saw that the lady's room was comfortable  

B. she saw the cups matched the saucers

C. the writer's slipcovers were very new  

D. the writer was preparing a big meal while she was too hungry

4. From the passage, we can infer that whether you are rich depends on __________.

A. how much money you have had    

B. how you have helped others

C. how you feel about your life      

D. what job your husband is doing

5. The writer left the muddy prints of small sandals on the floor for a while to __________.

A. show her husband that someone had come      

B. remind her that she had helped two children

C. remind her that she was very rich in the neighborhood  

D. remind her how life should be