问题 单项选择题

如图所示,光滑半球形容器固定在水平面上,O为球心,一质量为m的小滑块,在水平力F的作用下静止在P点。设滑块所受支持力为FN,OP与水平方向的夹角为θ。下列关系正确的是()

A.

B.F=mgtanθ

C.

D.FN=mgtanθ

答案

参考答案:A

解析:

画出物体的受力图,然后根据平行四边形定则及力的平衡条件,可看出:,选项A正确。

完形填空

根据短文内容及首字母提示,补全空格内单词,使短文完整、通顺。(请在答题卡上写出完整单词 )

Some years ago, I went to Australia for a meeting with my friend, Chris. We decided to drive across the country to Brisbane after the meeting ended. The drive was going to take four days and most of it was across the desert, so we had to take food, water, and extra gas(汽油) w  1  us.

The first day was a lot of fun as we were excited and laughing at each other’s jokes. By the third day of driving in the seemingly endless desert, we began to get b  2 . We had been quiet for a few hours when Chris found some kangaroos in the distance. We were b  3  excited and decided to get a closer look. Chris speeded up to

c  4  up with the kangaroos. We got closer and closer, and Chris was doing 110 kilometers per hour. We were very close to the kangaroos—too close—when we heard a loud BANG!

Chris s  5  the car and we got out. Behind the car was a larger kangaroo l  6  completely quiet on the ground. Chris went over to the kangaroo and put his baseball cap on its h  7 . He took off his sunglasses and put them on the kangaroo and did the same with his jacket. Then he put his arm a  8  the kangaroo and told me to take a photo of them together. I was still surprised, but I took out my c___9___. While I was ready to take photos, I saw the kangaroo move. It suddenly woke up, looked at Chris, and jumped away into the distance before we could do anything.

I started laughing but Chris looked very serious. He said his wallet and passport were in the jacket. I started laughing even harder. I stopped laughing, h  10 , when he said that our car keys were also in the jacket!

判断题