6.5 潜在能源

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  潜在能源

  

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  At what point does this diver have the most energy?
  ::这个潜水员哪一点最有能量?

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  This diver is going to jump from the end of the diving board. After they dive down and are falling toward the water, they’ll have , or the of moving matter. But even as they are momentarily stopped high above the water, they have energy. Do you know why?    
  ::这个潜水员将从潜水板的尽头跳下跳下。 当他们跳下水并坠落到水面时,他们就会有,或者移动物质。 但是,即使他们暂时停在水的顶端,他们也有能量。你知道原因吗?

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  Stored Energy
  ::存储能源

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  The diver has energy because of their position high above the pool. The type of energy they has is called potential energy. Potential energy  is energy that is stored in a person or object. Often, the person or object has potential energy because of its position or shape.
  ::潜水员拥有能量是因为其位置高在水库之上。他们拥有的能量类型被称为潜在能量。潜在的能量是储存在人或物体中的能量。通常,人或物体由于其位置或形状而具有潜在的能量。

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  Q: What is it about the diver’s position that gives them potential energy?
  ::问:潜水员的立场如何, 赋予他们潜在的能量?

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  A: Because the diver is high above the water, they have the potential to fall toward Earth because of gravity. This gives them potential energy.
  ::A:因为潜水员高在水面上, 它们有可能因为重力而掉向地球。 这使得它们具有潜在的能量。

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  Gravitational Potential Energy
  ::重力潜能能源

  

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  Potential energy due to the position of an object above Earth’s surface is called gravitational potential energy. Like the diver on the diving board, anything that is raised up above Earth’s surface has the potential to fall because of gravity. You can see another example of people with gravitational potential energy in the  Figure   .
  ::地球表面上方的物体位置造成的潜在能量被称为引力潜在能量。 与潜水板上的潜水员一样,在地球表面上方升起的任何能量都有可能因引力而下降。 你可以看到图中另一个具有引力潜在能量的人的例子。

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  Elastic Potential Energy
  ::弹性潜能能源

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  Potential energy due to an object’s shape is called  elastic potential energy . This energy results when an elastic object is stretched or compressed. The farther the object is stretched or compressed, the greater its potential energy is. A point will be reached when the object can’t be stretched or compressed any more. Then it will forcefully return to its original shape.
  ::由于物体的形状而形成的潜在能量被称为弹性潜在能量。 当弹性物体被拉长或压缩时,这种能量就会产生。 物体被拉长或压缩越远,其潜在能量就越大。 当物体无法拉长或压缩时,就会达到一个点。 然后,它就会强烈地回到原来的形状。

  

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  Shooting an arrow from a bow, as shown in the image , requires work done on the bow by the shooter's arm to bend the bow and thus produce potential energy. The release of the bow converts the potential energy of the bent bow into the kinetic energy of the flying arrow.
  ::从弓上射箭,如图象所示,需要枪手的手臂在弓上做工作才能弯曲弓,从而产生潜在的能量。弓的释放将弯弓的潜在能量转换成飞箭的动能。

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  Play around with the simulation below to adjust the stretch and elastic constant of a bow to see its effect on the motion of the arrow:
  ::用下面的模拟来调整弓的伸展和弹性常数, 以看到对箭头运动的影响 :

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  Other Forms of Potential Energy
  ::其他形式的潜在能源

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  If you hold two positive charges near each other, their  electromagnetic   potential energy  pushes them apart when you let go. Potential energy is stored in   ( chemical potential energy ). When these bonds are broken, the excess   is seen as molecular motion and  .
  ::如果你持有两个相互接近的正电荷, 他们的电磁潜在能量会把他们分开。 潜在的能量会储存在( 化学潜在能量 ) 。 当这些债券破裂时, 过剩的能量会被视为分子运动和分子运动 。

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  Calculating Potential Energy
  ::计算潜在能源

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  If a cannon ball is fired straight up into the air, it begins with a high kinetic energy. As the cannon ball rises, it slows down due to the force of gravity pulling it toward the earth. As the ball rises, its gravitational potential energy is increasing and its kinetic energy is decreasing. When the cannon ball reaches the top of its arc, its kinetic energy is zero and its potential energy is at the maximum. As gravity continues to pull the cannon ball toward the earth, the ball will fall downwards, causing its height to decrease and its to increase. The ball's potential energy decreases and its kinetic energy increases. When the ball returns to its original height, its kinetic energy will be the same as when it started upward.
  ::如果炮弹直接射向空中,它就会从高动能开始。当炮弹弹上升时,它会因引力而放慢速度,把它拉向地球。当球升起时,它的引力潜力正在增加,它的动能正在减少。当炮弹到达弧顶部时,它的动能是零,它的潜在能量是最大。当重力继续把炮弹拉向地球时,球会下降,导致它的高度下降,并增加。球的潜在能量减少,它的动能增加。当球回到原来的高度时,它的动能将和它开始向上时一样。

  

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  When work is done on an object, the work may be converted into either kinetic or potential energy. Work resulting in motion is caused when the work is converted into kinetic energy, while work resulting in a change of position is caused by a conversion into potential energy. Work is also spent overcoming and that work would be converted into , but we will consider primarily frictionless systems.
  ::当一个物体的工程完成后,该工程可以转换成动能或潜在能量。当工作转换成动能时,导致动能的工作即引起动能,而导致位置改变的工作则由于转换成潜在能量而引起。工作也花费了精力,而且工作将转换成......,但我们将主要考虑无摩擦的系统。

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  If we consider the potential energy of a bent stick or a stretched rubber band, the potential energy can be calculated by multiplying the force exerted by the stick or rubber band by the distance over which the force will be exerted. The formula for calculating this potential energy looks exactly like the formula for done:  $\begin{array}{r}W=Fd\end{array}$ . The only difference is that work is calculated when the object actually moves and potential energy is calculated when the system is still at rest, before any motion actually occurs.
  ::如果我们考虑弯曲棒或伸展的橡皮筋的潜在能量,那么潜在能量可以通过将棍棒或橡皮筋所施加的强度乘以所施力的距离来计算。计算这种潜在能量的公式与所施的公式完全相同:W=Fd。唯一的区别是,当物体实际移动和潜在能量计算时,当系统仍然处于休眠状态时,当任何运动实际发生之前,当系统仍然处于休眠状态时,当实际运动发生时,就会计算工作。

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  In the case of gravitational potential energy, the force exerted by the object is its and the distance it can travel is its height above the earth. Since the weight of an object is calculated by $\begin{array}{r}W=mg\end{array}$ , then gravitational potential energy can be calculated by $\begin{array}{r}PE=mgh\end{array}$ , where $\begin{array}{r}m\end{array}$ is the mass of the object,  $\begin{array}{r}g\end{array}$ is the , and $\begin{array}{r}h\end{array}$ is the height the object will fall.
  ::在引力潜在能量的情况下,物体所施加的力是它的,它可以飞行的距离是它在地球之上的高度。由于物体的重量由W=mg计算,那么引力潜在能量可以由PE=mgh计算,其中m是物体的质量,g是物体的高度,h是物体下落的高度。

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  Examples
  ::实例

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  Example 1  
  ::例1

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  A 3.00 kg object is lifted from the floor and placed on a shelf that is 2.50 m above the floor.
  ::3.00公斤物体从地板上举起,放在地板上方2.50米的架子上。

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  (a) What was the work done in lifting the object?
  :a) 在解除物体方面做了哪些工作?

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  (b) What is the gravitational potential energy of the object sitting on the shelf?
  :b) 坐在架子上物体的重力潜能能量是什么?

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   Answer
  ::答复答复答复

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  $\begin{array}{r}\text{weight of the object}=mg=(3.00kg)(9.80m/s^2)=29.4N\end{array}$
  ::物体的重量=mg=(3.00千克)(9.80米/秒)=29.4 N

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  (a) $\begin{array}{r}W=Fd=(29.4N)(2.50m)=73.5J\end{array}$
  :a) W=Fd=(29.4 N)(2.50米)=73.5 J

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  (b) $\begin{array}{r}PE=mgh=(3.00kg)(9.80m/s^2)(2.50m)=73.5J\end{array}$
  :b) PE=mgh=(3.00公斤)(9.80米/秒)(2.50米)=73.5J

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  Example 2  
  ::例2

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  A is constructed from a 7.58 kg bowling ball hanging on a 3.00 m long rope.  The ball is pulled back until the rope makes an angle of  $\begin{array}{r}{45}^{\circ }\end{array}$ with the vertical.
  ::A是用挂在3米长的绳子上的7.58公斤保龄球制成的,球被拉回,直到绳子的角为45英寸和垂直。

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  (a) What is the potential energy of the ball?
  :a) 球的潜在能量是什么?

  

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  You can use trigonometry to find the vertical height of the ball in the pulled back position.  This vertical height is found to be 0.877 m.
  ::您可以使用三角测量法在拉到的后方位置找到球的垂直高度。 垂直高度为 0. 877 米。

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  (a)  $\begin{array}{r}PE=mgh=(7.58kg)(9.80m/s^2)(0.877m)=65.1J\end{array}$
  :a) PE=mgh=(7.58公斤)(9.80米/秒)(0.877米)=65.1 J

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  A trampoline can store elastic potential energy just like a rubber band, spring or bow. The amount of energy stored relies on how far it is stretched. This energy is transferred into kinetic energy of the jumper as the are launched into the air. The energy is also converted into gravitational potential energy as the jumper gets higher and higher. Jump around in the simulation below to learn more:
  ::蹦床可以像橡胶带、弹簧或弓一样存储弹性潜在能量。 储存能量的量取决于它被拉长的程度。 随着跳跃器被射入空气,这种能量被转移到跳跃器的动能中。 随着跳跃器越高,这种能量也被转化成引力潜在能量。 跳跃器越高, 在模拟中跳跃到下面学习更多:

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  Further Reading
  ::继续阅读

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  Summary
  ::摘要

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  • Stored energy is called potential energy.
    ::存储能源被称为潜在能源。
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  • Energy may be stored by holding an object elevated in a gravitational field or by holding it while a force is attempting to move it.
    ::能源的储存方式可以是将一个物体放在重力场,或者在一股力量试图移动时将它放在重力场。
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  • Potential energy may be converted to kinetic energy.
    ::潜在的能源可以转换为动能。
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  • The formula for gravitational potential energy is $\begin{array}{r}PE=mgh\end{array}$ .
    ::引力潜在能量的公式是PE=mgh。
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  • In the absence of friction or bending, work done on an object must become either potential energy or kinetic energy or both.
    ::在没有摩擦或弯曲的情况下,就某一物体进行的工作必须成为潜在的能量或动能,或两者兼有。

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  Review
  ::回顾

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  1. A 90.0 kg man climbs hand over hand up a rope to a height of 9.47 m.  How much potential energy does he have at the top?
     ::A 90公斤的攀爬者 将绳索交到9.47米的高度。 他顶部有多少潜在的能量?
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  2. A 50.0 kg shell was fired from a cannon at earth’s surface to a maximum height of 400. m.
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     1. What is the potential energy at maximum height?
        ::最高高度的潜在能量是什么?
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     2. It then fell to a height of 100. m. What was the loss of PE as it fell?
        ::然后跌到100米高处。 当PE跌倒时损失了多少?
     
     ::一枚50公斤炮弹从火炮向地表发射,最高高度为400米。 最高高度的潜在能量是什么?然后跌到100米高度。 爆炸时丧失的PE是什么?
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  3. A person weighing 645 N climbs up a ladder to a height of 4.55 m.
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     1. What work does the person do?
        ::这个人做什么工作?
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     2. What is the increase in gravitational potential energy?
        ::引力潜在能量增加多少?
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     3. Where does the energy come from to cause this increase in $\begin{array}{r}PE\end{array}$ ?
        ::能源来自何方,
     
     ::体重为645N的人爬上梯子,达到4.55米的高度。 此人的工作是什么? 引力潜在能量的增加是什么? 能量来自何处,导致PE的增加?

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  Explore More
  ::探索更多

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  Use this resource to answer the questions that follow.
  ::使用此资源回答下面的问题 。

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  1. What is the definition of energy?
     ::能源的定义是什么?
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  2. Name two types of potential energy.
     ::列出两种潜在能源。
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  3. How is energy transferred from one object to another?
     ::能源如何从一个物体转移到另一个物体?