问题 选择题

如图所示的是常用指甲刀的实物及结构示意图,下列说法中不正确的是(  )

A.杠杆ABC是一个省力杠杆

B.杠杆D处刀刃较薄,是为了增大压强

C.杠杆ABC上有粗糙的花纹,是为了增大摩擦

D.指甲刀只有两个杠杆,一个省力杠杆和一个费力杠杆

答案

答案:D

题目分析:杠杆ABC的支点是B点,动力作用在A点,阻力作用在C点,使用时动力臂大于阻力臂,是省力杠杆,不符合题意,A错误;相同的压力下,D处刀口处是通过减小受力面积从而增大压强,不符合题意,B错误;杠杆ABC上有粗糙的花纹,通过增大接触面的粗糙程度,从而增大摩擦,不符合题意,C错误;指甲刀有三个杠杆,分别是杠杆ABC,由于动力臂大于阻力臂,属于省力杠杆;杠杆OBD和OED是两个费力杠杆,符合题意,选D。

点评:解决本题的关键是理解和分析指甲刀上的一些物理知识。

完形填空

Mr. King was the owner of a large company. 【3】 One day, he went into his office early in the morning to get ready to go to the airport and set out for a city.

He was leaving his office when Bill, a night watchman, came in Bill just came off work(下班). After saying “Good morning” to Mr. King, Bill told the owner about his bad dream. Last night he dreamed Mr. King’s plane crashed after it took off. Mr. King was surprised to hear this. He decided to go by land.

Bill’s dream came true. That morning the plane really crashed just after it had taken off. Later Mr. King returned to his office and heard the accident. To express his thanks, Mr. King gave Bill 5,000 dollars with a letter. 【4】Mr. King told Bill that a man like him should be sent away. Bill was surprised and asked, ”Why?” Mr. King said,” Go home and read the letter, and you will know why.”

Bill went home and opened the letter in a hurry. After he read it, he became sad. In the letter there is only one sentence. But it was enough to tell the reason.

任务一:根据短文回答问题

小题1:How did Mr. King feel after he heard Bill’s dream?

_________________________________________________.

小题2:What do you think the sentence in the letter could be?

_________________________________________________.

任务二:将文中划线部分翻译成汉语。

小题3:_______________________________________________.

小题4:_______________________________________________.

任务三:请给短文拟一个适当的题目

小题5:________________________________________________.

单项选择题