跟读练习: Statics: Lesson 46 - Distributed Loads Using Centroids - 通过视频学习英语口语

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153 句

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hey welcome back team today we're talking about distributed loads we've finished chapter set chapter 9

which was Centroids

and now I'm kind of going to jump you back to chapter 4 to talk about distributed loads

because really distribute loads I think it's kind of out of place until you talk about Centroids

and then they really make sense okay we know about Centroids center of volume, center of mass, center of area,

center of weight, center of pressure, right?

Distributed loads has a lot to do with that, okay?

So when you say a distributed load, what is a distributed load?

Well, it's like me standing on the floor, okay?

My weight is distributor over the size of my foot.

Or it's like this textbook.

If I lay this textbook on the table,

this textbook has weight, but that weight is not a point load or a concentrated load like we've been used to, right?

Like that.

That's what we're used to.

But this book actually has the weight spread out all over the whole thing

so that that weight is distributed across an area that's why we call it a distributed load some things

that you might see for

that um maybe maybe a snow load on a roof let's say you were designing a roof

or a building

and you needed to account for the snow load

now in texas where we are there we don't get a lot of snow

so we don't have to worry about that but

if you're up north then you have like a three or four foot storm that dumps that much snow

that could be a tremendous amount of weight on the roof.

If that kind of snow hit Texas,

it would collapse most buildings in Texas because they're just not designed to take that kind of weight on the roof.

So the distributed load looks something like this.

You'll see it given in some kind of weight per length.

In this case, 100 pounds per feet.

So for every foot I go, I'm going to accumulate 100 pounds of weight.

That's what the distributed load looks like.

And this is what we call a rectangular distributed load.

So it's even across the whole thing, okay?

So how do we deal with that?

I know how to deal with that, but I don't know how to deal with that, okay?

And so it would go something like this, right?

You would calculate the size of the distributed load by looking at how much of it you have.

So it's 100 pounds per feet over four feet.

So that would be 400 pounds.

And where do you apply that?

What we're doing here is we're converting a distributed load into a concentrated load just to simplify things

so that we can solve it as a regular old statics problem.

So that would be 400 pounds, right?

So you do 100 pounds per feet times four feet, right?

The feet cancel out and I'm left with just pounds, okay?

So that's where that comes from.

And then where do you apply it?

At the center, okay?

So distributed loads are all around us.

Let me give it to you this way.

Let's say that you want to go dancing, okay?

And you can go dancing, you can dance with me

or you could dance with lovely linda okay now i am full man size okay 220 pounds

that's full man size but lovely linda she's only 120 pounds okay

so who are you gonna dance with well before

we make up our mind let me tell you one thing me and Linda, we're both really bad dancers, okay?

And we're going to step on your foot, okay?

Now, I only go dancing in my cowboy boots, right?

And the heel of my cowboy boots is four inches by three inches, okay?

And so, lovely Linda, she only dances in her stiletto high heels because it makes her legs look good, you know what I mean?

And those little stilettos have a little high heel

that is a quarter of an inch by a quarter of an inch okay

now you're going to get stepped on i guarantee you that

because we're not that good at dancers okay

so let me tell you something you'll run into in solids

and that is stress okay

and stress is what we call the intensity of the force okay

so stress is p over a in other words the force divided by the area

that it's distributed over So in my case, you'd have 220 pounds divided by 3 times 4, 12 inches squared.

Now that's going to give me PSI, okay?

Where lovely Linda, lovely Linda over here is 120 pounds divided by a quarter times a quarter.

That is 0 .0625 inches squared.

And let's see what we get here.

So, if you're dancing with me, you get 220 divided by 12, you're going to feel 18 .3 PSI, okay?

but if you're dancing with linda over there 120 divided by 0 .0625 you're going to feel

1 ,920 psi okay now i don't know what the sheer stress of skin is

but you may be you know if i step on you it's going to hurt

but if she steps on you she may be standing on the floor like through your foot, right?

Punctured a hole right in you.

So, that's distributed load.

If you take a big load and you distribute it over a bigger area, the intensity of the force is much less,

whereas a smaller load even over a very small area, the intensity of the load is very high, okay?

So, when do we see this kind of stuff in real life?

Let's say, I've got me a truck drawn over here.

Let's say you go to the hardware store, okay?

You're building a new house and they're going to deliver it to you

and so what they do is they go out

and they stack up two by fours okay

and two by fours look like this okay and let's say that two by fours were i don't know

500 pounds per foot

and then the little guy at the hardware store thought he'd be clever

there was going to be some cinder blocks on there

so he stacked them like up high but then he went every row, he stacked them one less.

So he had like this triangular load here.

Okay.

Very clever little brick stacker guy.

And what we do on triangular loads is we only give you the tallest point.

So let's say that's 700 pounds per foot.

100

At this end, it's zero pounds per feet, isn't it?

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And then, I don't know, for some reason on that job site, they also were asking for a whole pallet full of helium okay maybe helium

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and so that load is like this 200 pounds per feet

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but it's going upwards right it's it's pulling upwards okay so

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and if we look at this you might say well okay

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uh find the reactions on the tires okay

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so we could say over here maybe we have a by and then over here,

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I have an AY, and I could solve for those reaction forces on those tires

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if I can convert those distributed loads into concentrated loads.

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Well, this first one, let me just, let me, let's make up some numbers here.

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This looks like 15 feet.

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I'm going to do numbers that I can do in my head.

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How about that?

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20 feet.

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Okay.

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And this is 20 feet, which would make this back here 13 feet.

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Okay.

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It's a 53 foot trailer.

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That's how long, that's how long most flatbed tractor trailers are, 53 feet.

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Okay.

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So this bit up here is 500 times 20.

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That's going to be 10 ,000, isn't it?

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And where would I apply that?

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Right there.

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So that's 10 ,000 pounds.

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And I would apply that right in the center of

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that rectangle because the centroid of a rectangle is half the base, right?

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Then this guy, and all I'm doing, think about this as an area.

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Think about the 500 as the height, and the 20 as the width, and I'm finding the area.

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You can't go out with a tape measure and measure that area, but it's an area, okay?

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This area here is 700 tall by 20, but it's a triangle, so I'm going to treat it like an area.

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I've got to divide that by two, so that would be like 700 times 10, which would be 7 ,000.

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And where would you put that 7 ,000 pounds?

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Well, I put it like right there.

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Okay.

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Why right there?

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Well, it's at one third the base of the triangle, right?

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So this distance right here would be 20 over three.

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Okay.

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That's centroid stuff, isn't it?

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and then over here oh the only tricky part about this is the arrows are going up instead of down

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so this is 200 times 13 which would be 2600 and I would put that right there Okay.

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2 ,600 pounds.

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And it's in the middle of the 13.

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And so now, now I've got three concentrated loads where I used to have distributed loads.

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I can solve that like a regular old statics problem, right?

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Take the moment at A and I got 400 times two rotating me negative.

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I got 500 times six rotating me negative plus BY times seven rotating me positive

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and just solve it like every problem we've done.

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So distributed load problems should be really easy for you if you know what a centroid is,

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because all you gotta do is calculate the area of this shape, 100 times four, right?

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Apply that load at the centroid of that shape and then just work it like a regular old statics problem, okay?

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So when I come back, we'll work one of those problems in the next video and maybe that'll make more sense to you.

153

So hope that helps.

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✨ 推荐视频

45 句

本课的词汇与口语要点

这节口语课以视频“Statics: Lesson 46 - Distributed Loads Using Centroids”为素材。视频中反复出现的词有：load, distributed, pounds, feet, weight。这段视频共有 153 个句子、1627 个单词可供跟读。讲话部分时长为 10:42。说话人语速自然，每分钟约 152 个词，接近日常对话。 86% 的单词属于英语最常用的 3,000 词，其余的词建议在练习前先学一下。全部 153 个句子中有 40 个是问句，适合练习疑问语调和简短回答。

视频中的重点词汇

视频中 15 个值得学习的单词，附发音和释义：

单词	发音	释义
distribute 动词	/dɪˈstɹɪbjuːt/	分配
divide 动词	/dɪˈvaɪd/	分, 分裂
solve 动词	/sɒlv/	解決 /解决
concentrate 动词	/ˈkɑn.sən.tɹeɪt/	集中
intensity 名词	/ɪnˈtɛnsɪti/	強度 /强度, 強烈 /强烈
stack 名词	/stæk/	堆
heel 名词	/hil/	腳跟 /脚跟, 後跟 /后跟
textbook 名词	/ˈtɛkst.bʊk/	課本 /课本, 教科書 /教科书
rotate 动词	/ˈɹoʊ.teɪt/	旋转, 转动
trailer 名词	/ˈtɹeɪlɚ/	拖車 /拖车
hardware 名词	/ˈhɑɹdˌwɛɹ/	硬件, 硬體 /硬体
boot 名词	/but/	靴子, 長靴 /长靴
tire 动词	/ˈtaɪ̯ɚ/	勞累 /劳累, 累
dancer 名词	/ˈdænsəɹ/	舞蹈家, 舞蹈演員 /舞蹈演员
triangle 名词	/ˈtɹaɪˌæŋɡəl/	三角, 三角形

视频中出现的短语动词

单词	发音	释义
make up 动词	/ˌmeɪk ˈʌp/	組成 /组成
come back 动词		回來 /回来, 返回
go out 动词		出, 出口
go up 动词		上昇 /上升, 上去

值得反复跟读的句子

视频中简短而完整的句子，可以直接用在日常对话里：

That's what we're used to.
Let's say that you want to go dancing, okay?
Let's say you go to the hardware store, okay?
That's centroid stuff, isn't it?

需要注意的发音

说话人用了 47 次缩略和弱读形式，例如 I'm, we're, you're。请按听到的简短形式来说。

长单词——注意重音位置: intensity /ɪnˈtɛnsɪti/, rectangular /ɹɛkˈtæŋɡjəlɚ/, triangular /tɹaɪˈæŋ.ɡjə.lɚ/, accumulate /əˈkjuːmjʊˌleɪt/

中文母语者容易读错的音：

/v/ — 不要读成 /w/，上齿轻触下唇: divide /dɪˈvaɪd/, solve /sɒlv/, clever /ˈklɛv.ɚ/, convert /kənˈvɝt/
词尾辅音 — 要读清楚，后面不要加元音: distribute /dɪˈstɹɪbjuːt/, pound /ˈpaʊ̯nd/, divide /dɪˈvaɪd/, solve /sɒlv/, concentrate /ˈkɑn.sən.tɹeɪt/
/r/ 和 /l/ 的区别: trailer /ˈtɹeɪlɚ/, triangle /ˈtɹaɪˌæŋɡəl/, rectangular /ɹɛkˈtæŋɡjəlɚ/, rectangle /ˈrɛktæŋɡl̩/, triangular /tɹaɪˈæŋ.ɡjə.lɚ/

如何用这段视频练习

先完整听一遍视频，不要开口，记下不认识的单词。
先用 0.75 倍速逐句跟读，熟练之后再回到正常速度。
录下自己的声音并与原声对比，特别注意 distribute, divide, solve 这类单词。

什么是跟读法？

跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。

影子跟读法: 阅读完整分步指南 →

跟读练习: Statics: Lesson 46 - Distributed Loads Using Centroids - 通过视频学习英语口语

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本课的词汇与口语要点

视频中的重点词汇

视频中出现的短语动词

值得反复跟读的句子

需要注意的发音

如何用这段视频练习

什么是跟读法？