シャドーイング練習: Statics: Lesson 46 - Distributed Loads Using Centroids - 動画で英語スピーキングを学ぶ

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153 文

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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?

101

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

102

and so that load is like this 200 pounds per feet

103

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

104

and if we look at this you might say well okay

105

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

108

if I can convert those distributed loads into concentrated loads.

109

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.

112

How about that?

113

20 feet.

114

Okay.

115

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

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Okay.

117

It's a 53 foot trailer.

118

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

119

Okay.

120

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?

130

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

131

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

132

And where would you put that 7 ,000 pounds?

133

Well, I put it like right there.

134

Okay.

135

Why right there?

136

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

137

So this distance right here would be 20 over three.

138

Okay.

139

That's centroid stuff, isn't it?

140

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

141

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.

143

And it's in the middle of the 13.

144

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

145

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

146

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

148

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

149

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

150

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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このレッスンの語彙とスピーキングのポイント

このスピーキングレッスンは、動画「Statics: Lesson 46 - Distributed Loads Using Centroids」を教材にしています。繰り返し出てくる語は次のとおりです：load, distributed, pounds, feet, weight。この動画には、シャドーイング用の文が153文、単語が1627語あります。音声の長さは10:42です。話す速さは1分あたり約152語で、日常会話に近い自然なペースです。単語の86%は英語の頻出3,000語に含まれます。残りは練習の前に確認しておきましょう。全153文のうち40文が疑問文なので、疑問文のイントネーションや短い受け答えの練習に向いています。

この動画の重要語彙

動画に出てくる覚えておきたい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
distribute 動詞	/dɪˈstɹɪbjuːt/	分ける
divide 動詞	/dɪˈvaɪd/	分割する, 分ける
solve 動詞	/sɒlv/	解決する
concentrate 動詞	/ˈkɑn.sən.tɹeɪt/	集中させる
intensity 名詞	/ɪnˈtɛnsɪti/	強度
stack 名詞	/stæk/	塚
heel 名詞	/hil/	踵, ヒール
textbook 名詞	/ˈtɛkst.bʊk/	教科書, テキスト
rotate 動詞	/ˈɹoʊ.teɪt/	回る
trailer 名詞	/ˈtɹeɪlɚ/	トレーラー
hardware 名詞	/ˈhɑɹdˌwɛɹ/	ハードウェア, ハード
clever 形容詞	/ˈklɛv.ɚ/	巧い
boot 名詞	/but/	ブーツ, ブート
tire 動詞	/ˈtaɪ̯ɚ/	疲れる
dancer 名詞	/ˈdænsəɹ/	ダンサー, 舞踊家

動画に出てくる句動詞

単語	意味
come back 動詞	戻る, 帰る
go out 動詞	出る
go up 動詞	上がる, 登る

繰り返し練習したい文

動画に出てくる短く完結した文です。日常会話でそのまま使えます。

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?

注意したい発音

話し手はI'm, we're, you'reなど、短縮形や弱形を47回使っています。聞こえたとおりの短い形で発音しましょう。

長い単語（アクセントの位置に注意）: intensity /ɪnˈtɛnsɪti/, rectangular /ɹɛkˈtæŋɡjəlɚ/, triangular /tɹaɪˈæŋ.ɡjə.lɚ/, accumulate /əˈkjuːmjʊˌleɪt/

日本語話者が苦手な音：

/r/ と /l/ の区別 — /l/ は舌先を歯茎につけ、/r/ はどこにもつけない: trailer /ˈtɹeɪlɚ/, triangle /ˈtɹaɪˌæŋɡəl/, rectangular /ɹɛkˈtæŋɡjəlɚ/, rectangle /ˈrɛktæŋɡl̩/, triangular /tɹaɪˈæŋ.ɡjə.lɚ/
/v/ — /b/ にならないように、上の歯を下唇に当てる: divide /dɪˈvaɪd/, solve /sɒlv/, clever /ˈklɛv.ɚ/, convert /kənˈvɝt/
/f/ — 「フ」ではなく、上の歯と下唇で出す: flatbed /ˈflætˌbɛd/, simplify /ˈsɪmplɪfaɪ/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
まず0.75倍速で一文ずつシャドーイングし、慣れてきたら通常の速度に戻します。
自分の声を録音して元の音声と比べます。distribute, divide, solveなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: Statics: Lesson 46 - Distributed Loads Using Centroids - 動画で英語スピーキングを学ぶ

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このレッスンの語彙とスピーキングのポイント

この動画の重要語彙

動画に出てくる句動詞

繰り返し練習したい文

注意したい発音

この動画での練習方法

シャドーイングとは？英語上達に効果的な理由