问题 填空题

星期天小星帮妈妈包馄饨时使用圆柱形的擀面杖是为了减小______;煮一段时间后,馄饨渐渐浮起,在浮起过程中馄饨受到的浮力______重力,同时水面上漂着油花,这是因为油的______比水小.

答案

圆形的擀面杖在擀面时,与面接触的只是靠近面圆弧的切线部分,这样将滑动摩擦变为滚动摩擦,从而减小摩擦力;

馄饨浮起是一个上浮的过程,在这个过程中,馄饨受到两个力的作用:浮力和重力,根据物体的浮沉条件,所以浮力大于重力.

漂浮在水面上的油受到的浮力等于重力,即F=G.根据阿基米德原理可知FgV;物体的重力GgV.

所以,ρgVgV.由于漂浮,所以V小于V.由此可知:油的密度小于水的密度.

故答案为:摩擦力;大于;密度.

阅读理解

A new supermarket put on a notice inside the entrance. It said, “Remember, once a week, one of our customers(顾客) gets free goods(things that cost nothing). This may be your lucky day!” All the housewives who went to the supermarket had one great hope: to be the lucky customer who didn’t have to pay for her shopping.

For several weeks Mrs. Blake hoped to be the lucky customer. Unlike many other customers, she never gave up hope. The cupboards in her kitchen were full of things she did not need. She dreamed of the day, when the manager of the supermarket would come and say to her, “Madam, this is your lucky day and everything in your basket is free.”

One Friday morning, after she finished her shopping and had taken all the things to her car, she found that she had forgotten to buy tea. She went to the supermarket, got the tea and went towards the check-out. As she did so, she saw the manager of the supermarket come to her. “Madam,” he said, “congratulations! You are our lucky customer and everything in your basket is free!”

小题1:From the notice in the new supermarket, we know that       .

A.customers could buy things at lower prices once a week

B.the customer who bought the least goods didn’t have to pay

C.just one customer could get free goods once a week

D.the first customer who bought goods in the supermarket was the lucky one小题2: What was Mrs. Blake’s hope?

A.To buy something cheaper in the supermarket.

B.To see the manager of the supermarket.

C.To buy everything she needed in the supermarket.

D.To be the lucky customer.小题3: Why did Mrs Blake go back to the market after her shopping?

A.Because she wanted to see who would be the lucky customer.

B.Because she forgot to buy one more thing.

C.Because she had to pay for her shopping.

D.Because she wanted to get another chance to be the lucky customer.小题4:Which of the following is NOT TRUE according to the passage?

A.The manager of the market was a clever businessman.

B.In fact the notice for free goods was a trick (诡计).

C.Mrs. Blake’s dream came true at last.

D.Mrs. Blake did shopping every week in the past several weeks.小题5:What would Mrs. Blake probably say when she heard the manager’s words?

A.“Oh, my God!”

B.“How lucky I am!”

C.“Bad luck!”

D.“It’s very kind of you!”

单项选择题