问题 填空题

如图所示,质量为M的物体靠在粗糙的竖直墙上,物体与墙面的动摩擦因数为 μ.现用垂直于斜边的推力F作用于物体上,物体保持静止状态,则物体受到墙面的摩擦力为______.

答案

如图建立坐标系对M进行受力分析:

M受重力、支持力FN,摩擦力f,推力F.

由于M静止在墙面上,故处于平衡状态满足平衡条件:

y轴方向:f-Mg-Fsinθ=0         

解得:f=Mg+Fsinθ

故答案为:Mg+Fsinθ

阅读理解

阅读理解。

      Peter was a small boy. He lived with his parents in a small house near some hills. The people there

were all poor. One night it was very dry and windy. When everybody was asleep, Peter suddenly heard

some noise. It came out from the kitchen (厨房). He got up and walked to the kitchen. He found that the wood beside the stove (火炉)  was burning. There was no water tap (水龙头) in the house,so he could

not put out (扑灭) the fire. He shouted loudly to wake up everyone in the house. Then he ran out of his

house and knocked on the doors of many houses to wake the people up. They all left their houses quickly.At last the fire was put out by the firemen. Many houses were hurt. But nobody was hurt in the fire.

1. Peter lived with his_____.      

A. sisters                  

B. brothers

C. uncles                  

D. parents

2. One night he found that_____beside the stove was burning.      

A. the table              

B. the wood

C. the door                

D. the window

3. _____, so he could not put out the fire.       

A. Everybody was asleep

B. He couldn't shout loudly

C. The kitchen was very big

D. There was no water tap in the house

4. Peter knocked on the doors of many houses _____.        

A. to wake the people up

B. to get some water

C. to find his classmates

D. to visit the people

5. _____hurt in the fire.      

A. People in other houses were

B. Peter's parents were

C. Nobody was

D. Peter was

单项选择题