题干

图中所示的情景中,关于力对物体做功的叙述,正确的是(   )

A:举重运动员举着杠铃不动.运动员对杠铃做功了

B:起重机吊着重物上升.钢绳竖直向上的拉力对重物做功了

C:人推汽车但没有推动.人的推力对汽车做功了

D:足球在水平地面上滚动.足球受到的重力对足球做功了

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答案(点此获取答案解析)

B

同类题5

阅读下面短文, 掌握其大意, 然后从各题所给的A、B、C、D四个选项中选出最佳选项。

    A boy thought that he was the most unhappy person in the world. In his opinion, he was unlucky because almost everything 1always happened to him. He wanted to find the 2 to happiness. He walked a long way and finally came to a beautiful palace. There, he met the king.

    After learning 3 the boy came, the king suggested that he should look around the palace and come back in two hours. “At the same time, I want you to hold this spoon 4 milk,” said the king. “As you walk around my palace, carry this spoon 5 without spilling the milk.”

    The boy kept his eyes fixed on the spoon and began to walk around the golden palace. After two hours, he came back to the king. “Well,” asked the king. “Did you 6 the wonderful paintings in my dining hall? Did you enjoy the colorful flowers in the garden?” The boy felt sorry because he saw 7.  He only paid attention to the milk.

    "Then go back and you can see the beauty of my world.” said the king. This time the boy saw all of the works of art on the walls. He saw the great gardens and hills all around. He had a great time 8 he was walking around the palace. When he 9, he described everything he saw.

     "But where is the milk?” asked the king. Looking down at the spoon he held, the boy saw the milk was gone. “Well, there is only one piece of 10 I can give you,” said the king. “The secret to happiness is to see all the beauty of the world and also keep an eye on the milk on the spoon.”