问题 选择题

曲线运动中,合速度(       )

A.一定大于分速度

B.一定小于分速度

C.一定等于分速度

D.可能大于分速度

答案

答案:D

合速度大小与两个分速度的大小以及分速度间的夹角大小有关,可能大于、小于或等于分速度。所以答案选D。

阅读理解

根据短文内容,判断下列句子的正误,正确的用"T",错误的用"F"。

       A farmer's dog, Dolly, had puppies (小狗), and the farmer needed to sell them. He painted a sign and

   put it in his yard. As he was putting up the sign, a little boy walked up to him.

       "Sir," he said, "I want to buy one of your dogs. "

       "Well, " said the farmer, "these dogs are very expensive. "

       "Can I just look.'?" asked the boy.

       "Sure," said the farmer and whistled (吹口哨). "Here, Dolly !" he called.

       Dolly ran out from the doghouse and four little dogs followed her. The boy became excited.

       Then, the little boy noticed another dog. This one was smaller. It moved slowly and tried to catch up

  with the others.

       "I want that one," the boy said, pointing to the little dog.

       The farmer said, "Son, you don't want that dog. He will never be able to run and play with you like

  these other dogs. "

       The little boy reached down and rolled up (卷起) one leg of his trousers. He showed a cast (石膏)

  on his leg and a specially made shoe. He said, "You see, sir, I don't run too well myself, and he will need

  someone who understands. "

       The world is full of people who need someone who understands.

( ) 1. Dolly was a mother dog which bad four baby dogs.

(     ) 2. One of the dogs moved slowly probably because its legs were weak.

(     ) 3. The farmer advised the boy not to choose the smaller dog.

(     ) 4. Nothing was wrong with the boy's leg.

(     ) 5. We learn from the story that one should show love and understanding for the weak.

单项选择题