问题 多选题

关于质点,下列说法中正确的是(  )

A.质点是为了研究问题方便而建立的理想化模型

B.研究旋转的铁饼飞出的距离时,铁饼可以看成质点

C.研究体操运动员在空中的动作时,运动员可以看成质点

D.研究“神舟”六号飞船绕地球飞行的轨道时,飞船可以看成质点

答案

A、质点是忽略了物体的形状和大小,把物体看成一个具有质量的点,这是为了研究问题方便而建立的理想化模型,所以A正确;

B、研究旋转的铁饼飞出的距离时,铁饼的形状和大小可以忽略,能看成是质点,所以B正确;

C、研究体操运动员在空中的动作时,人的形状是不能忽略的,所以此时的运动员不能看成质点,所以C错误;

D、研究“神舟”六号飞船绕地球飞行的轨道时,飞船的大小事可以忽略的,所以此时飞船可以看成质点,所以D正确.

故选ABD.

阅读理解

阅读理解。

     Some children are flying kites near the river. They are very high and Peter can see them in the classroom.

His mother's friend Mrs White comes to see his mother this morning and brings a kite to him. She gives it to

him after lunch. It looks like a bird. He wants to fly it but his mother doesn't let him do so.

     "It's time to go to school," says the woman,"or you will be late for class. You can play it after school."

The boy is sorry, but he says goodbye to Mrs White and goes to school. Now he's in the classroom but he's

looking out. He doesn't listen to Miss Black. She writes something on the blackboard and then turns to the

class.

     "Name nine things with milk in them, Peter," she says.

     The boy doesn't hear her and still sits there. A boy after him taps his back and he understands it. He stands

up and Miss Black asks him the question again. He thinks for some time and then says, "Yes, madam, tea,

coffee, cake and… er… six cows."

1. Where is Peter when some children are flying kites?

A. Near the river.

B. In the classroom.

C. At home.

D. At Mrs White's home.

2. Mrs White comes to see Peter's mother _________.

A. this morning

B. this evening

C. after lunch

D. this afternoon

3. Mother lets Peter fly the kite after school and _________.

A. tells him to go to school

B. tells him to do the homework

C. they begin to have lunch first

D. tells him to listen to the teacher

4. Peter looks out of the classroom, so _________.

A. he wants to go home

B. he can answer the question

C. he doesn't hear Miss Black

D. he can fly a kite

5. Peter only knows _________.

A. six cows

B. three things with milk in it

C. how to fly a kite

D. tea and coffee

单项选择题 B型题