题干

小李和小红同学研究“使用动滑轮缓慢提起重物时所需竖直向上的拉力F与哪些因素有关”,他们用如图所示装置,将不同物体缓慢提起,分别测出物体所受重力G和所需拉力F的大小,数据记录在表一中.然后,他们更换滑轮,重复实验,将相关数据记录在表二、表三中.

表一:G滑轮=1.0牛

实验

序号

G

(牛)

F

(牛)

1

2.0

1.5

2

2.5

1.8

3

3.0

2.0

4

4.0

2.5

表二:G滑轮=2.0牛

实验

序号

G

(牛)

F

(牛)

5

2.5

2.3

6

3.0

2.5

7

3.5

2.8

8

4.0

3.0

表三:G滑轮=3.0牛

实验

序号

G(牛)

F(牛)

9

4.0

3.5

10

5.0

4.0

11

6.0

4.5

12

7.0

5.0

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同类题5

阅读下面短文,从每题所给的 A、B、C、D 四个选项中选出最佳选项。

D

    Kathy could still remember the night she had to leave her home in Hungary. It was the beginning of World War II and her family had to leave their country as soon as possible. She quickly filled a bag with a few pieces of clothing, her diary, and her treasure—a beautiful silk scarf.

    Kathy and her best friend, Monica, had asked their parents to buy them matching scarves. They each would wear the scarves as a symbol of their friendship. Kathy had no idea that she was going to America that night and would not be returning.

    Kathy kept that special silk scarf for many years. One day she decided to give it to her granddaughter, Eliza, to wear to her first job interview for good luck. Kathy was afraid that Eliza would lose the scarf, but the granddaughter promised, “Don't worry, Grandma, nothing's going to happen to your scarf. You'll see. It is going to bring both of us luck today.” And with that, Eliza kissed her grandmother and left for the interview.

    That afternoon Eliza left the interview, feeling sure that she had got the job. So she decided to celebrate by going to a restaurant. As she was sitting at her table, she felt someone looking at her. Sitting next to her was an old woman, who could not take her eyes away from her.

    “I'm sorry, do I know you?” Eliza asked.

    “I'm sorry, dear, but you make me think of someone I once knew,” the old woman replied. “My best friend looked like you and used to wear a scarf just like the one you're wearing around your neck.” Eliza listened carefully, with her eyes and mouth wide open. She had heard stories of her grandmother's best friend and knew the meaning of the scarf. Could this be Monica, her grandmother's childhood friend?

    Eliza introduced herself and waited to hear the name of the other woman.

    “My name's Monica, dear. I lived in Hungary as a child, but my family had to leave when I was fourteen years old. I've been living here in California ever since.” said the old woman.

    Eliza could not believe her ears …