问题 问答题

如图所示,质量m=2kg的木块P放在质量M=8kg的水平木板上,木板与地面间的动摩擦因数μ=0.5.向左抽动木板时木块P处于静止状态,此时测力计的指针指在4N处,g取10m/s2

(1)木块与木板间的动摩擦因数是多少?

(2)向左需用多大的力F可将木板匀速抽出?

答案

(1)木块受到的滑动摩擦力f=4N                   

木块与木板间的动摩擦因数μ1=

f
mg
=
4
2×10
=0.2

(2)向左匀速抽出,需要克服木块和地面的摩擦力    

F=f+μ(m+M)g=4+0.5(2+8)10=54N

答:(1)木块与木板间的动摩擦因数是0.2.

(2)向左需54N的力可将木板匀速抽出.

阅读理解

阅读短文,根据要求完成下面各小题。

     Failure (失败) is a part of life. No matter what we do, there are always two results: success and failure.

There is no doubt (怀疑) that every one of us wants to be successful, but we can't always avoid failure.

     People have different opinions about the failure. Some people regard failure as a bad thing. They hold

that they should always do everything well. If they fail in something, they will lose their confidence. Other

people regard failure as a chance to learn. They redo (重做) what they failed to do. They know complaining

won't help themselves.

     As an old saying goes, "Failure is the mother of success." As long as we keep to what is right and correct

what is wrong in time, we will have success. In my opinion, failure is not bad, it's not good, either.

1. Failure can make people lose their confidence. (T or F)

    ______________________________

2. Life without failure isn't true. (T or F)

    ______________________________

3. Put the underlined sentence (in Paragraph 1) into Chinese.

                                                                                   

4. Why do some people regard failure as a chance to learn?

    _____________________________________________

5. What does the writer think about failure?

                                                                                   

解答题