问题 填空题

用弹簧测力计在空气中称得一石块重为lN,将石块完全浸入水中,弹簧测力计的示数为0.6N,则石块在水中受到的浮力为_________N,石块的体积为________cm3。(取g=10N/kg)

答案

0.4   40

题目分析:由题意可知,两次弹簧测力计示数差为0.4N,由力的平衡知识可知,石块在水中受到的浮力为0.4N;

由阿基米德原理可知,石块所受浮力的大小等于石块排出水的重力,故石块排出水的重力为0.4N;

由公式

点评:解决此类题目要利用阿基米德原理及浮力公式,结合力的平衡知识去求解分析.

阅读理解

阅读理解。

A: The wind is blowing lightly (轻轻地). I really love this weather.

B: Me, too.

A: Let's fly a kite.

B: Good idea.

(A few minutes late)

A: Look at the sky, Jack. The clouds are moving quickly.

B: Good. The wind is getting stronger. Look, our kite is high in the sky.

A: Hold the kite tightly (紧紧地), Jack. The wind is getting stronger and stronger.  

B: The wind is too strong now. Look, a lot of leaves (树叶) are falling from the trees.

A: Don't look at the leaves. Get our kite back.

B: The string on our kite breaks (断). Oh, no! It's flying away.

A: The sky is getting dark. I'm very afraid.

B: Let's go home.                          

1. What's the weather like in the beginning?

A. It's fine.      

B. It's rainy.        

C. It's windy.        

D. It's snowy.

2..The ______ becomes dark when they are flying a kite.

A. Cloud        

B. Sky            

C. Wind            

D. Kite

3..What happens to their kite when the wind blows strongly?

A. It flies higher and higher.            

B. It gets back.

C. It flies away.                      

D. It falls in a tree.

4..A lot of ______ fall when the wind blows strongly.

A. fruits        

B. birds            

C. kites            

D. leaves

5..From the dialogue, we know a ______ will come when they are flying a kite.

A. fine day  

B. storm (暴风雨)    

C. snow          

D. flood (洪水)

单项选择题