쉐도잉 연습: Statics: Lesson 46 - Distributed Loads Using Centroids - 영상으로 영어 말하기 배우기

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hey welcome back team today we're talking about distributed loads we've finished chapter set chapter 9
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which was Centroids
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and now I'm kind of going to jump you back to chapter 4 to talk about distributed loads
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because really distribute loads I think it's kind of out of place until you talk about Centroids
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and then they really make sense okay we know about Centroids center of volume, center of mass, center of area,
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center of weight, center of pressure, right?
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Distributed loads has a lot to do with that, okay?
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So when you say a distributed load, what is a distributed load?
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Well, it's like me standing on the floor, okay?
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My weight is distributor over the size of my foot.
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Or it's like this textbook.
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If I lay this textbook on the table,
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this textbook has weight, but that weight is not a point load or a concentrated load like we've been used to, right?
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Like that.
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That's what we're used to.
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But this book actually has the weight spread out all over the whole thing
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so that that weight is distributed across an area that's why we call it a distributed load some things
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that you might see for
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that um maybe maybe a snow load on a roof let's say you were designing a roof
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or a building
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and you needed to account for the snow load
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now in texas where we are there we don't get a lot of snow
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so we don't have to worry about that but
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if you're up north then you have like a three or four foot storm that dumps that much snow
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that could be a tremendous amount of weight on the roof.
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If that kind of snow hit Texas,
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it would collapse most buildings in Texas because they're just not designed to take that kind of weight on the roof.
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So the distributed load looks something like this.
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You'll see it given in some kind of weight per length.
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In this case, 100 pounds per feet.
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So for every foot I go, I'm going to accumulate 100 pounds of weight.
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That's what the distributed load looks like.
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And this is what we call a rectangular distributed load.
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So it's even across the whole thing, okay?
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So how do we deal with that?
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I know how to deal with that, but I don't know how to deal with that, okay?
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And so it would go something like this, right?
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You would calculate the size of the distributed load by looking at how much of it you have.
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So it's 100 pounds per feet over four feet.
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So that would be 400 pounds.
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And where do you apply that?
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What we're doing here is we're converting a distributed load into a concentrated load just to simplify things
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so that we can solve it as a regular old statics problem.
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So that would be 400 pounds, right?
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So you do 100 pounds per feet times four feet, right?
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The feet cancel out and I'm left with just pounds, okay?
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So that's where that comes from.
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And then where do you apply it?
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At the center, okay?
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So distributed loads are all around us.
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Let me give it to you this way.
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Let's say that you want to go dancing, okay?
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And you can go dancing, you can dance with me
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or you could dance with lovely linda okay now i am full man size okay 220 pounds
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that's full man size but lovely linda she's only 120 pounds okay
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so who are you gonna dance with well before
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we make up our mind let me tell you one thing me and Linda, we're both really bad dancers, okay?
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And we're going to step on your foot, okay?
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Now, I only go dancing in my cowboy boots, right?
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And the heel of my cowboy boots is four inches by three inches, okay?
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And so, lovely Linda, she only dances in her stiletto high heels because it makes her legs look good, you know what I mean?
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And those little stilettos have a little high heel
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that is a quarter of an inch by a quarter of an inch okay
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now you're going to get stepped on i guarantee you that
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because we're not that good at dancers okay
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so let me tell you something you'll run into in solids
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and that is stress okay
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and stress is what we call the intensity of the force okay
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so stress is p over a in other words the force divided by the area
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that it's distributed over So in my case, you'd have 220 pounds divided by 3 times 4, 12 inches squared.
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Now that's going to give me PSI, okay?
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Where lovely Linda, lovely Linda over here is 120 pounds divided by a quarter times a quarter.
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That is 0 .0625 inches squared.
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And let's see what we get here.
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So, if you're dancing with me, you get 220 divided by 12, you're going to feel 18 .3 PSI, okay?
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but if you're dancing with linda over there 120 divided by 0 .0625 you're going to feel
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1 ,920 psi okay now i don't know what the sheer stress of skin is
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but you may be you know if i step on you it's going to hurt
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but if she steps on you she may be standing on the floor like through your foot, right?
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Punctured a hole right in you.
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So, that's distributed load.
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If you take a big load and you distribute it over a bigger area, the intensity of the force is much less,
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whereas a smaller load even over a very small area, the intensity of the load is very high, okay?
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So, when do we see this kind of stuff in real life?
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Let's say, I've got me a truck drawn over here.
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Let's say you go to the hardware store, okay?
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You're building a new house and they're going to deliver it to you
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and so what they do is they go out
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and they stack up two by fours okay
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and two by fours look like this okay and let's say that two by fours were i don't know
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500 pounds per foot
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and then the little guy at the hardware store thought he'd be clever
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there was going to be some cinder blocks on there
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so he stacked them like up high but then he went every row, he stacked them one less.
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So he had like this triangular load here.
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Okay.
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Very clever little brick stacker guy.
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And what we do on triangular loads is we only give you the tallest point.
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So let's say that's 700 pounds per foot.
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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.
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So hope that helps.

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이 레슨의 어휘와 말하기 포인트

이 말하기 레슨은 영상 “Statics: Lesson 46 - Distributed Loads Using Centroids”을(를) 바탕으로 합니다. 가장 자주 반복되는 단어는 다음과 같습니다: load, distributed, pounds, feet, weight. 이 영상에는 섀도잉할 문장 153개와 단어 1627개가 있습니다. 말하는 구간의 길이는 10:42입니다. 화자는 분당 약 152단어로, 일상 대화에 가까운 자연스러운 속도로 말합니다. 단어의 86%가 영어에서 가장 많이 쓰이는 3,000단어에 속합니다. 나머지는 연습 전에 미리 확인해 두세요. 전체 153문장 중 40문장이 질문이어서 의문문 억양과 짧은 대답을 연습하기에 좋습니다.

이 영상의 핵심 어휘

영상에 나오는 익혀 둘 만한 단어 15개를 발음, 뜻과 함께 정리했습니다.

단어발음뜻
divide 동사/dɪˈvaɪd/나누다, 가르다
solve 동사/sɒlv/해결하다
intensity 명사/ɪnˈtɛnsɪti/강도
stack 명사/stæk/무더기
heel 명사/hil/발뒤꿈치, 발뒤축
textbook 명사/ˈtɛkst.bʊk/교과서, 텍스트북
trailer 명사/ˈtɹeɪlɚ/트레일러
hardware 명사/ˈhɑɹdˌwɛɹ/하드웨어, 굳은모
boot 명사/but/장화, 목화
tire 동사/ˈtaɪ̯ɚ/피곤하다
dancer 명사/ˈdænsəɹ/댄서, 춤꾼
triangle 명사/ˈtɹaɪˌæŋɡəl/삼각, 삼각형
calculate 동사/ˈkælkjʊleɪt/정산하다, 계산하다
cowboy 명사/ˈkaʊˌbɔɪ/카우보이
guarantee 명사/ˌɡæɹ.ənˈtiː/보증

영상에 나오는 구동사

단어뜻
come back 동사돌아오다
go out 동사나가다
go up 동사올라가다

따라 말해 볼 만한 문장

영상에 나오는 짧고 완결된 문장으로, 일상 대화에서 그대로 쓸 수 있습니다:

  • 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?

주의할 발음

화자는 I'm, we're, you're 같은 축약형과 약화된 형태를 47번 사용합니다. 들리는 대로 짧게 발음하세요.

  • 긴 단어 — 강세 위치에 주의: intensity /ɪnˈtɛnsɪti/, rectangular /ɹɛkˈtæŋɡjəlɚ/, triangular /tɹaɪˈæŋ.ɡjə.lɚ/, accumulate /əˈkjuːmjʊˌleɪt/

한국어 화자가 어려워하는 소리:

  • /f/ — ㅍ(/p/)으로 바꾸지 말고 윗니를 아랫입술에 대기: flatbed /ˈflætˌbɛd/, simplify /ˈsɪmplɪfaɪ/
  • /v/ — ㅂ(/b/)과 구별하기: divide /dɪˈvaɪd/, solve /sɒlv/, clever /ˈklɛv.ɚ/, convert /kənˈvɝt/
  • /z/ — ㅈ이 아니라 성대를 울리는 /s/: upwards /ˈʌpwɚdz/, whereas /(h)wɛɹˈæz/

이 영상으로 연습하는 방법

  1. 먼저 말하지 않고 영상을 끝까지 듣고 모르는 단어를 적어 둡니다.
  2. 0.75배속으로 한 문장씩 섀도잉을 시작하고, 익숙해지면 보통 속도로 돌아갑니다.
  3. 자신의 목소리를 녹음해 원본과 비교하고, divide, solve, intensity 같은 단어에 특히 주의합니다.

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