问题 填空题

老虎钳是电工常用的一种工具,通过观察你会发现其中应用了许多物理知识,请说出两个物理知识:

(1)______.

(2)______.

答案

(1)力学:钳子是个省力杠杆;钳口有花纹,是增大接触面的粗糙触电增大摩擦力;钳子把有花纹是增大接触面的粗糙程度增大摩擦力;

(2)电学:钳子是钢制的,钢是导体;钳子把套有橡胶皮,橡胶皮是绝缘体,使用时防止触电.

故答案为:

(1)钳把套上有花纹,增大接触面的粗糙程度增大摩擦力;

(2)钳把套有橡胶皮,橡胶皮是绝缘体防止触电.

单项选择题
阅读理解

阅读短文,选出最佳答案。                         

Nick Petrels is a doctor in Montreal. He works 60 hours a week. He takes care of 159 patients a week in the hospital and at his office. He’s been a doctor for ten years.

Dr. Petrels gives his patients good medical advice. But he doesn’t just tell his patients what to do. He also sings to them on television! Dr. Petrels has his own TV show. The show is in Italian, English and French. The doctor starts the show with a song and then gives medical advice. He explains a medical problem or disease in simple language. After that, he sings another song.

Dr. Petrels produces and performs in his own show every week. The program is very popular with his patients and with people who enjoy his singing. His dream is to perform(表演) in Las Vegas. His favorite songs are love songs, and he has a compact disk of love songs that he wrote. Dr. Petrels says, “I always loved to sing. All my problems are gone when I sing.” But when Dr. Petrels was young, his father didn’t want him to be a singer, so he went to medical school.

Some people tell Dr. Petrels he can help people more as a doctor. But Dr. Petrels says he helps people when he sings, too. “I like to make people smile. Sometimes it’s difficult to make a sick person smile. Medicine and entertainment(娱乐) both try to do the same thing. They try to make people feel good.”

1. Dr. Petrels works 60 hours a week, because he _______.

A. gives his patients medical advice      B. takes care of 159 patients a week

C. sings on television                  D. has his own TV show

2. Dr. Petrels _______, so he is called a singing doctor. 

A. has been a doctor for ten years       B. always loved to sing

C. is popular with his patients          D. also sings to his patients on TV

3. In his TV show, Dr. Petrel _______.

A. sings and gives medical advice         B. sings about different diseases

C. starts to explain diseases with a song    D. sings love songs he wrote

4. Dr. Petrels’ show is popular _______.

A. in Las Vegas.                   B. at medical school  

C. with people who like his singing    D. with patients in Montreal  

5. Dr. Petrels says he likes to _______.

A. help people sing          B. make people feel better 

C. do the same thing         D. make difficult people smile