问题 选择题

在《探究求合力的方法》实验中,如图甲表示在两个力F1和F2的共同作用下,将橡皮条GE拉长到O点;图乙表示只用一个力F将橡皮条GE拉长到O点;图丙是用力的图示表示F1、F2和F。则我们之所以认为F是F1和F2的合力是因为

A.力F大于F1、F2

B.力F在平行四边形的对角线,而F1、F2在邻边

C.F 、F1和F2这三个力符合平行四边形定则

D.力F的作用效果与F1、F2的共同作用效果相同

答案

答案:D

F1和F2的共同作用与只用一个力F都将橡皮条GE拉长到O点,作用效果相同,所以我们才认为F是F1和F2的合力,D对。

阅读理解

阅读理解

       I was one of the seven children and went to the same school as my three elder sisters and brothers.

We all went to the plant sale held in early May every year, just in time for Mother's Day.

       When I was in Grade Three, I wanted to surprise my mother with a gift, but I didn't have any money. My elder sister gave me some. I carefully made my selection(选择)  at the plant sale.  I looked at all the

plants on sale very carefully and finally chose a lovely geranium (天竺葵).  Once I had brought it home, I

hid it on the neighbor's porch (门廊).

       On Mother's Day,  I was bursting (突然打开) with pride when I gave her the plant. I remember how bright her eyes were, and how pleased she was with my gift.

       A few years later, my younger sister wanted to buy a geranium for our mother. As my elder sister did

for me, I gave her some money to buy one at the plant sale. She arrived back from the sale full of nervous excitement. The geranium was hidden in a paper bag under her sweater, "I looked at every plant,"  she

explained,  ' and I know I got the best one ! "

       With a sweet sense of family tradition(惯例) , helped my little sister hide that geranium. I was there

when she gave it to my mother, and I watched them both bursting with happiness. My mother noticed me watching. She gave me a soft, secret smile. I felt a tug(拽) at my heart as I smiled back.  I wondered how my mother could pretend to be surprised at this gift from her sixth child. But as I watched her eyes light up with pleasure at the sight of the most special gift, I knew she was not pretending.

1. Which of the seven children was the writer?

A. The third.          

B. The fourth.

C. The fifth.          

D. The sixth.

2. What did the children go to the plant sale for? 

A. To buy their mother a gift.

B. To sell some flowers.

C. To make money for their mother.

D. To look at all the plants.

3. Why did the writer hide the geranium on the neighbor's porch? 

A. Because she was afraid the other children saw it.

B. Because she was afraid the others stole it.

C. Because she wanted to make it live a long time.

D. Because she wanted to give their mother a surprise.

4. "She gave me a soft, secret smile" shows that

A. the mother was very surprised

B. the mother knew about it

C. the mother was pretending to be happy

D. the mother knew the writer bought the gift

5. What's the best title of the passage?

A. Mother's Day

B. Lovely Mother

C. The Most Special Geranium

D. Mother's Love

单项选择题