题干

如图所示,发射地球同步卫星时,先将卫星发射至近地圆轨道1,然后经点火使其沿椭圆轨道2运行,最后再次点火将卫星送入同步圆轨道3.轨道1、2相切于Q点.轨道2、3相切于P点(如图),则当卫星分别在1、2、3轨道正常运行时,下列说法中不正确的是(   )

A:卫星在轨道3上的周期小于在轨道1上的周期

B:卫星在轨道3上的速率小于在轨道1上的速率

C:卫星在轨道2上运行时,经过Q点时的速率大于经过P点时的速率

D:卫星在轨道2上运行时,经过Q点时加速度大于经过P点的加速度

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答案(点此获取答案解析)

A

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    I live with my grandmother in a Beijing yard house. One day last year, I was surprised to see a big foreigner coming out of the house next door to ours. He was very tall with short brown hair and a pair of glasses.

    The first time I saw him, I was too shy to speak to him. “My English is too poor!” I thought. My grandmother told me that he had just moved into our yard. “I don't like it!” she said. “Foreigners aren't like us. Maybe he'll play loud music and parties every night! I'm sure he's going to cause trouble.”

    Several days later, I met the foreigner as I was walking home after work. “Hello!” he said (in Chinese!). “My name's Tony. I've just moved into the house next door to yours.” While I was wondering what to say, he continued, “There's a nice bar down the road. Why don't you and your family come and have dinner with me?” “Bars are bad places,” said my grandmother when I told her, but we decided to go.

    The bar was not at all what I had expected. It was in a beautiful little yard house, with several large bookshelves and pictures of Tibet on the walls. Several Chinese people and foreigners were sitting drinking or reading books. I noticed that some of the foreigners were speaking Chinese in a low voice to each other! “Oh, what a civilized place!” my grandmother exclaimed.

    The bar served special “hutong pizzas”. As we ate, Tony told us about himself-he is an English expert in environment. He always likes to be quiet. My grandmother said to me, “He really seems like a very nice young man.”