用绳悬挂一个质量为1 kg的木块，木块重心到悬点的距离为1 m，质量为10 g的
题型：问答题
问题：
用绳悬挂一个质量为1 kg的木块，木块重心到悬点的距离为1 m，质量为10 g的子弹以500 m/s的速度水平射入木块并以100 m/s的速度水平穿出.求子弹射穿木块的瞬间，绳中的张力为多大？
题型：问答题
第三节 阅读理解（共20小题，每小题2分，满分40分）
阅读下列四篇短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上将该项涂黑。
A
An eight-year-old child heard her parents talking about her little brother. All she knew was that he was very sick and they had no money. Only a very expensive operation could save him now and there was no one to lend them the money.
When she heard her daddy say to her tearful mother, “Only a miracle can save him now,” the little girl went to her bedroom and pulled her money from its hiding place and counted it carefully.
She hurried to a drugstore with the money in her hand.
“And what do you want?” asked the salesman. “It’s for my little brother,” the girl answered. “He’s really, really sick and I want to buy a miracle.” “Pardon?” said the salesman.
“My brother Andrew has something bad growing inside his head and my daddy says only a miracle can save him. So how much does a miracle cost?” “
We don’t sell a miracle here, child. I’m sorry,” the salesman said with a smile.
“Listen, if it isn’t enough, I can try and get some more. Just tell me how much it costs.”
A well-dressed man heard
it and asked, “What kind of a miracle does your brother need?”
“I don’t know,” she answered with her eyes full of tears. “He’s really sick and mum says he needs an operation. But my daddy can’t pay for it, so I have brought all my money.”
“How much do you have?” asked the man. “$ 1.11, but I can try and get some more,” she answered.
“Well, what luck,” smiled the man. “$ 1.11, the price of a miracle for little brothers.”
He took up the girl’s hand and said, “Take me to where you live. I want to see your brother and meet your parents. Let’s see if I have the kind of miracle you need.”
That well-dressed man was Dr Carlton Armstrong, a famous doctor. The operation was successful and it wasn’t long before Andrew was home again.
How much did the miracle cost?
36．What was the trouble in the little girl’s family?
A．Her brother was seriously ill. B．They had no money.
C．Nothing could save her brother. D．Both A and B.
37．In the eye of the little girl, a miracle might be .
A．something interesting B．something beautiful
C．some wonderful medicine D．some good food
38．The little girl said again and again “...I can try and get some more.” That shows .
A．she had still kept some money
B．she hoped not to be refused
C．There was no need to worry about money
D．she thought money was easy to get
39．What made the miracle happen?
A．The girl’s love for her brother． B．The girl’s money.
C．The medicine from the drugstore. D．Nobody can tell.
40．From the passage we can infer(推断) that______
A．the doctor didn’t ask for any pay
B．a miracle is sure to happen if you keep on
C．the little girl is lovely but not so clever
D．the doctor had great sympathy for the girl’s little brother