题干

2013年12月2日,嫦娥三号探测器顺利发射,其轨道示意图如图所示.“嫦娥三号”升空约18min后进入地月转移轨道,在P点经过近月制动,进入离月球表面100公里的环月圆轨道Ⅰ,之后再次变轨,从环月圆轨道Ⅰ降低到椭圆轨道Ⅱ,两轨道相交于点P.若绕月运行时只考虑月球引力作用,关于“嫦娥三号”探测器,以下说法正确的是(   )

A:在轨道Ⅰ上经过P点的速度大于在轨道Ⅱ上经过P点的速度

B:在轨道Ⅰ上经过P点的加速度小于在轨道Ⅱ上经过P点的加速度

C:从轨道Ⅰ变轨到轨道Ⅱ,“嫦娥三号”必须点火减速

D:在环月圆轨道Ⅰ上运行时处于超重状态

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答案(点此获取答案解析)

A,C

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    After you get back home from a trip, one of the most pleasant things is sharing your stories with people. And that's what we'd like you to do. Our magazine's “True Stories” section is for your strange experiences, heart-warming tales and funny stories on your trip. So if you have good stories, please write to us!

    If your story is chosen as the best one, you will win the nine-day trip across North America, including a seven-night trip along the California coast. For more information, please call 800-227-2826, or e-mail us at TrueStories@hotmail.com.

    Besides, you need to remember a few things if you want to write a story:

    Keep the story brief (简短的) and lively (within 250 words).

    Please send your story as the body of your e-mail, not as an attachment (附件).

    Most of the stories we print have photos, so send pictures, but try not to go crazy. Send only the best one(s).

    Please send your photos as an attachment, not embedded in (把……嵌入) the body of your e-mail.

    We don't mind if you or your friends are in the pictures, as long as you tell us who or what is in the photos.

    We need to be able to get in touch with you, so tell us your phone number and home address.

Information about the magazine

“True Stories” section

About ____, heart-warming tales and funny stories on the trip.

Writing a great travel story

Prize

A nine-day trip across North America, including a(n) ____ trip along the California coast.

____

●The story should____

●Send it as the body of the e-mail.

●Send the best ____.

●Send your photos as an attachment.

●Tell us who or what is in your pictures.

●Tell us your phone number and home address.