工作 工作 工作 工作

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For some, the exciting part of a roller coaster is speeding down; for others it is the anticipation of climbing up. While the coaster is being towed up, it is having work done on it. The work done towing it to the top of the hill becomes stored in the coaster and that potential energy is converted to as the coaster runs down from the top of the hill to the bottom.
::对一些人来说,过山车的令人兴奋的部分正在加速下降;对另一些人来说,这是爬升的预期。当海岸车被拖上来的时候,它正在完成它的工作。把它拖到山顶的工作被储存在海岸车内,而随着海岸车从山顶向下运行,潜在的能量被转换为从山顶向下运行。

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Work
::工作 工作 工作 工作

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The word work has both an everyday meaning and a specific scientific meaning. In the everyday use of the word, work would refer to anything which required a person to make an effort. In physics , however, work ( W ) is defined as the transferred when a force ( F ) is applied to move an object over a ( d ). This can be calculated by multiplying the force exerted on an object by the distance the object moves due to that force, or $\begin{array}{r}W=Fd.\end{array}$
::工作一词既具有日常含义,又具有特定的科学含义。在日常使用该词时,工作是指需要一个人努力的任何事物。但在物理学中,工作(W)的定义是,当用一种力量(F)将物体移到a(d)上时,工作(W)被转移到了工作(F),这可以通过物体因该力量而移动的距离乘以物体所承受的力,或W=Fd来计算。

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In the scientific definition of the word, if you push against an automobile with a force of 200 N for 3 minutes but the automobile does not move, then you have done no work. Multiplying 200 N times 0 meters yields zero work. If you are holding an object in your arms, the upward force you are exerting is equal to the object’s . If you hold the object until your arms become very tired, you have still done no work because you did not move the object in the direction of the force. When you lift an object, you exert a force equal to the object’s weight and the object moves due to that lifting force. If an object weighs 200. N and you lift it 1.50 meters, then your work is  $\begin{array}{r}W=Fd=(200.\text{N})(1.50\text{m})=300.\text{N m}\end{array}$ .
::在对这个词的科学定义中,如果用200N的力对着一辆汽车推力三分钟,但汽车没有移动,那么你没有做任何工作。乘以200N乘以0米等于零工作。如果在你的手臂中持有物体,你的上方力等于物体。如果你在手臂中持有物体,你的上方力等于物体。如果你在手臂中保持物体,直到你的手臂非常疲惫,你仍然没有做任何工作,因为你没有将物体移动到力的方向。当你举起物体时,你施加的力等于物体的重量和物体因推力而移动的力。如果物体重量为200.N和抬升1.50米,那么你的工作就是W=Fd=200.N(1.50米)=300米。

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One of the units you will see for work is shown above: the Newton meter (Nm). More often, however, units of work are given as the  Joule (pronounced "jool") in honor of James Prescott Joule, a nineteenth century English physicist. A Joule is a kg·m ² /s ² . 
::以上列出了您将看到的工作单位之一:牛顿计(Nm)。然而,更常见的情况是,工作单位被定为Joule(宣布为“jool”),以纪念19世纪英国物理学家James Prescott Joule(19世纪的英国物理学家)的James Prescott Joule。Joule是一个k.m2/s2。

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Example 1
::例1

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A boy lifts a box of apples that weighs 185 N. The box is lifted a height of 0.800 m. How much work did the boy do?
::男孩抬起一盒重185牛顿的苹果。 盒子被抬高0.800米。 男孩做了多少工作?

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$\begin{array}{r}W=Fd=(185\text{N})(0.800\text{m})=148\text{N m}=148\text{Joules}\end{array}$
::W=Fd=(185 N)(0.800米)=148 N=148 焦耳

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Work is done only if a force is exerted in the direction of motion. If the motion is perpendicular to the force, no work has been done. If the force is at an angle to the motion, then the component of the force in the direction of the motion is used to determine the work done.
::如果该动议与武力无关,则没有完成任何工作;如果该动议处于动议的角度,则以动议方向的部队组成部分决定完成的工作。

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Example 2
::例2

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Suppose a 125 N force is applied to a lawnmower handle at an angle of 25° with the ground and the lawnmower moves along the surface of the ground.  If the lawnmower moves 56 m, how much work was done?
::假设在25°角的草坪上对割草机把手施用125 N 力,地面角为25°,割草机沿着地面移动。 如果割草机移动了56米,那么做了多少工作?

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The solution requires that we determine the component of the force that was in the direction of the motion of the lawnmower because the component of the force that was pushing down on the ground does not contribute to the work done.
::解决办法要求我们确定朝着割草机运动方向前进的部队组成部分,因为推倒在地面的部队组成部分无助于已完成的工作。

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$\begin{array}{r}{F}_{\text{parallel}}=(\text{Force})(\cos {25}^{\circ })=(125\text{N})(0.906)=113\text{N}\end{array}$
::Fparallel=(部队)(cos25)=(125N)(0.906)=113N

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$\begin{array}{r}W=F_{\text{parallel}}d=(113\text{N})(56\text{m})=6328\text{J}\end{array}$
::W=Fplalleld=(113 N(56米)=6328 J)

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Getting a piano into a truck isn't easy, so we often use a ramp to lower the amount of required force. Although the force is smaller, the distance we have to apply the force is greater. So in a way, we exchange force for distance. However, the total amount of work done remains the same. Play around with the Ramp and Piano SIM below to learn more:
::把钢琴送进卡车并不容易,所以我们经常使用斜坡来降低所需武力的数量。虽然部队规模较小,但我们必须使用部队的距离要大一些。因此,在某种程度上,我们用部队换距离。然而,完成的工程总量仍然不变。与下面的Ramp和Piano SIM一起玩耍,学习更多:

 

 

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Summary
::摘要

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• Work is the force exerted on an object multiplied by the distance the object moves due to that force.
  ::工作是对物体施加的力乘以物体因该力而移动的距离。
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• The unit for work is called the joule, which is a kg m ² /s ² .
  ::工作单位称为焦耳,为kgm2/s2。
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• If the force is at an angle to the motion, then the component of the force in the direction of the motion is used to determine the work done.
  ::如果武力处于动议的一个角度,则以动议方向的部队组成部分来确定已完成的工作。

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Review
::回顾

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1. How much work is done by the force of gravity when a 45 N object falls to the ground from a height of 4.6 m?
   ::当45N物体从4.6米高处坠落到地面时,重力做了多少工作?
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2. A workman carries some lumber up a staircase.  The workman moves 9.6 m vertically and 22 m horizontally.  If the lumber weighs 45 N, how much work was done by the workman?
   ::工人在楼梯上携带一些木材。工人垂直移动9.6米,水平移动22米。如果木材重45牛顿,工人做了多少工作?
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3. A barge is pulled down a canal by a horse walking beside the canal.  If the angle of the rope is 60.0°, the force exerted is 400. N, and the barge is pulled 100. m, how much work did the horse do?
   ::一艘驳船在运河旁行走的马把一条运河拉下。如果绳子的角是60.0度,那么所施加的力量是400度。 N,驳船拉下100米,马做了多少工作?

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Explore More
::探索更多

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The following video introduces energy and work. Use this resource to answer the questions that follow.
::以下影片介绍能量和工作。 使用此资源回答下面的问题 。

 

 

 

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1. How can mechanical energy be added to or removed from a system?
   ::如何将机械能源添加或从系统中去除?
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2. How can you use a Force vs Displacement Graph to derive the work done on a system?
   ::您如何使用“强制对流离失所图”来获取系统完成的工作?