题干

如右图所示,一物体在水平恒力作用下沿光滑水平面做曲线运动,当物体从M点运动到N点时,其速度方向恰好改变了90°,则在此过程中,该物体的动能将(       )

A:不断增大

B:不断减小

C:先减小后增大

D:先增大后减小

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答案(点此获取答案解析)

C

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完形填空

    One year my children came home from school asking where we were going on your summer vacation. It seemed that all the other kids were1 where they were spending the summer. I couldn't 2to take them anywhere but I didn't want to tell them that so I just said, “It's a surprise!” They were 3. That bought me a little more 4.

    I called several amusement 5to see if there was a half-price event during the summer but no such 6. I tried everything, with no success, so I called some of the other moms to find that most were in the same7that I was. We decided to8 something fun for our kids to do. We had a meeting, all five of us, and9 what is now called a “playcation”.

    One mother was a  10, so on Mondays the kids would all go to her house. They would play games using plants and11. They also planted vegetables and12 them grow over the summer.

    Another mother had Bible 13 on Tuesdays. She asked some questions about Bible. The kid who answered  14got a penny, which they all turned in at the end to buy their goodie bags(礼品袋).

    At our house on Wednesdays, I made an outdoor 15training with my spare tires. The kids also walked a balance beam and raced through large cardboard boxes taped together.

    On 16they had arts and crafts across the street. Fridays were17by a wonderful single dad with a metal detector(金属探测器)who took everyone out treasure18 .

    The summer was a big19 . Okay, it wasn't Disney World,20 the kids didn't miss anything. My son actually asked me, “Can we do this again next year?”