In this episode, let's talk about the relationship between the force and objects ,

這集我們談力量與物體之間的關係

first this blue is an object,

首先藍色這個是物體

it has contains both are convex and concave,

它有包含了凸面和凹面

and also relatively wider and narrower parts,

還有比較寬廣和狹窄的部分

when after the concept of the objects enters, we will to produce the proportional scale,

當物體的概念進入後，我們會產生比例尺

the unit is what that not the focus,

單位是什麼並非重點

this an object is subjected to variety of different roles by the forces and moment couple now,

現在這個物體受到各種不同的力和力偶矩的作用

so it produced a certain the deformation,

所以它產生了一定的變形

and the dashed line is the object line after it's deformed,

而虛線就是它變形後的輪廓線

maybe it still will start to moves or rotations after thrust surface,

也許它受力之後還會開始移動或轉動

the force will causes objects the moves dip direction,

力量會使物體移動傾向...

the moment couple will causes objects to have rotates dip direction,

力偶矩則使物體產生轉動傾向

the soil mechanics did not use to the moment couple,

土壤力學並沒有用到力偶矩

so it will not appear again after this episode appears.

所以在這集出現後就不再出現

that, we consider of the objects are also not rotation occurs ,

而我們考慮的物體也都不會發生轉動

because the soil will not rotation,

因土壤不會轉動

ok, next let's take a look at the force.

好接下來我們來看一下力量

first, we can see it withstand the concentrated force of F1

首先我們可以看到它承受F1的集中力

and the force of F2

和F2的力量

there are also f1 and f2

另外有f1和f2

the uniform force and distributed force,

均佈力和分佈力

that, let's explain the nouns now,

那現在我們來作名詞解釋

focusing on role by the object on 1 point is called the concentrated force,

集中於物體1點上作用者稱作集中力

the concentrated force can act on or outside the objects,

集中力可作用於物體上或物體之外

can be understood as the force at a distance, (but actually is vector movement), that's no problem,

可以當作超距力理解(但其實是向量移動)，並無問題

the force of unit we use is Newton N,

力量我們使用的單位是牛頓N

the concentrated force actually is abstract concept,

集中力其實是抽象概念

assume the force acts on a certain particle,

假定了力量作用在某一質點

this particle doesn't exist in the real world,

此質點在現實世界中並不存在

the force of real world must be demonstrated in the distributed force manner,

現實世界的力量一定是以分佈力的方式去展現

even if you poke the potato with one needle,

哪怕你用一根針戳馬鈴薯

the tip also has certain area,

針尖也是有一定的面積

next, let's look at the distributed force,

接下來我們來看分佈力

the distributed force can be called uniformity force in certain case,

分佈力在某個情況下可以稱作均佈力

that is, it the same with role of "density"form on a certain acreage,

就是它在一定面積上作用的"密度"是一樣的

that used here was is similar to the concept of density,

這裡使用的是類似於密度的概念

the distributed force unit actually is how many Newtons is acts on per square meter,

分佈力單位其實是每平方公尺上面作用多少牛頓

actually also is mean the how many Newtons is acts on each unit area,

其實也是每單位面積上作用多少牛頓的意思

in fact, the distribution force can be equivalent to the concentrated force,

其實分佈力可以等效於集中力

the equivalent manner is as follows:

等效方式如下：

first to consider this the uniform force ,

先考慮此均佈力

the density of the uniform force is f2

均佈力的密度是f2

the interaction length is l2,

作用長度為l2

what is the equivalent concentrated force of such a force?

如此的等效集中力是多少呢？

write the concentrated force as the red arrow,

集中力寫成紅色箭頭

it's value = f2 * l2

其值=f2*l2

then multiply the unit area is 1

再乘上單位面積是1

this 1 can be as length of paper surface prominence,

這個1可以當作突出紙面的長度

we use angle of the three dimension to see is so

我們用三維的角度來看就是如此

so it acts on an area,

所以它作用於一面積上

the magnitude by the concentrated force is the volume of the rectangular parallelopiped,

集中力大小就是長方體體積

i.e f2*l2*1

即f2*l2*1

where is such a the concentrated force acting?

那這樣的集中力作用在哪裡呢？

acting on above the centroid of the rectangle,

作用在長方型的形心上面

the centroid is in the middle...so we draw the concentrated force right here,

形心在中間...所以我們把集中力畫在這裡

point of application in about 1/2l2 the place,

作用點在大約1/2l2的地方

another one distributed force is the triangle,

另外一個分佈力是三角形

in fact, the distributed force can have any shape,

其實分佈力可以有任何形狀

the triangle...that accordance with the rectangle,

三角形...就比照長方形

the magnitude is the bottom multiplied by the height divided by two

大小就是底乘以高除以二

point of application in 1/3l1 the place,

作用點位置在1/3l1的地方

when in the exam, we used to take the uniform force

在考試的時候我們習慣把均佈力

to calculates after change to the concentrated force,

改成集中力後再來計算

because for the objects ,them are equivalent ,

因為它們對物體來說是等效的

the so-called the equivalent is the same with the effect of generated,

所謂等效就是產生的效應是一樣的

that let's consider a question now.

那我們現在來考慮一個問題

what happens after an object is cuts ?

將物體切開以後會發生什麼事？

we know the object is for the maintain its shape before the thrust surface,

我們知道物體為了維持自己受力前的形狀

when subjected to external forces, internal forces are also will generated within the object,

當受外力的時候，物體內部也會產生內力

so soil mechanics is defined...

所以力學就是定義了...

the force that can be observed before cutting is the external force

切開前可觀察的力為外力

the force that emerges after being cut is called the internal force.

切開後才顯現的力量叫作內力

the internal force is actually very complicated,

內力其實非常的複雜

and with the angle or way you cut,

而且隨著你切開的角度或方式

the internal forces generated both are also different,

所產生的內力也都不一樣

the internal forces must have appeard with form of distributed forces,

內力一定是以分佈力的形式出現

it main can be divided into two types,

它主要可以分作兩種

one is the normal stress and one is the tangential stress,

一種是正向應力，一種是剪應力

the so-called the normal stress is the direction of stress vertical to the section,

所謂正向應力就是應力方向垂直於切面

the so-called the tangential stress is the direction of stress parallel to the section,

所謂剪應力就是應力方向平行於切面

such as red arrows

如紅色的箭頭

the external force and internal force are gives to objects...

那外力和內力對於物體...

effects produced are not the same,

產生的效應並不一樣

what's the effects produced of the external force?

外力產生的效應是什麼呢？

has movement, rotation, reaction force, work and so on ...

有移動、轉動、反作用力、作功...等等

for the internal force, it will make the...

內力來說的話，它會使的...

the stress in the object changes,

物體裡面的應力產生變化

deformation, transformation energy...and so on.

變形、能量變化...等等

for in soil mechanics...

在土壤力學來說...

when the external force continue to increase in the case, the internal force will rise accordingly,

外力不斷增加的情況下，內力也會相應上升

the normal stress in the soils will causes soil consolidation,

土壤內的正向應力會使的土壤壓密

that is the density increases (strength rises),

也就是密度增加(強度上升)

the increase of the tangential stress will make the the general shear failure of soils,

剪應力的上升則會使土壤剪力破壞

the main form of soil damage is the general shear failure,

土壤主要的破壞形式就是剪力破壞

finally, let's supplement the concept of "the rigid body",

最後我們來補充「剛體」的概念

the rigid body is considered as the ideal objects for the internal effects are not exist.

剛體視為內效應不存在之理想物體

can imagine the rigid body don't exist in the real world,

可以想見剛體並不存在於現實世界中

within the subjects of engineering mechanics is

在工程力學的科目裡面

the objects are all assumed be the rigid bodies,,

物體都被假設為剛體

that is, only the effects of external and external effects are considered,

也就是只考慮外力和外效應的影響

the material mechanics will considered of internal force the part,

而材料力學則會考慮內力的部分

then the soil mechanics is builted on top of these two subjects,

土壤力學又建立在二科之上

so the scope of consideration is will again broader,

所以考慮的面向又更廣了

ok, the above is all the content today. Bye ~

以上就是今天全部的內容~~掰掰~~