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液体内部存在压强,如图,烧杯内盛有密度为ρ的液体,我们可以设想液面下h深处有一底面积为S的水平圆面,它所受到的压力是其上方圆柱形的小液柱所产生的.

(1)请推证:液体内部深度为h处的压强p=ρgh;

(2)已知圆柱形下表面所在深度为30cm,所受压强为3.6×103Pa,则液体的密度是多少?

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答案(点此获取答案解析)

解:
(1)证明:小液柱的体积:V=Sh,
∴小液柱的质量:m=ρV=ρSh,
小液柱的重力:G=mg=ρShg,
小液柱对底面积S的压力:F=G=mg=ρShg,
小液柱产生的压强:p=
F
S
=

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                                                                                          How Not to Do It All

    We all want to do so much: complete our never ending list of tasks and projects, help everyone, travel everywhere, learn a lot of new skills, read every book and watch every good film. ____ There isn't enough time in the day, nor do we have much attention to devote to everything.

    Give up on trying to do it all. ____ It is important for you to make your days count(有价值). How do you do that? Here are some ideas:

    ____ When you eat a good meal, it's wasted if you actually ignore(不理会)it and are reading on your phone instead. It's an amazing meal only if you really enjoy it. In this way, if we enjoy each moment, they really matter.

    Be satisfied. We always want to do more, be more, experience more. And so, we're never satisfied with the little we actually can do and experience. Instead, we should learn to be happy with what we've chosen to do, knowing that we let go of the rest for a reason. ____

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A. Pay attention.

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D. Put only the best things in each day.

E. Don't try to have the most perfect life you can create.

F. We can accept the reality that is exposed when we let go.

G. We should be thankful for what's actually in front of us and the experience we are given.