Posted on Categories:Thermodynamics, 热力学, 物理代写

物理代写|热力学代写Thermodynamics代考|Potential energy

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物理代写|热力学代写Thermodynamics代考|Potential energy

Potential energy is the form of energy associated with a mass at an elevation above a reference frame. The mass has the potential to do work by moving downward in a gravitational field. Often the reference frame for potential energy is the ground, but it can be between any two vertical elevations.
You can calculate the potential energy $(P E)$ of an object with mass $(m)$ at elevation $(z)$ above the reference frame with the gravitational acceleration $(g)$, using this equation:
$$P E=m \cdot g \cdot z$$
Suppose you’re winding up your grandfather clock. The weights are 2 kilograms each, and you raise them up by 30 centimeters. You can figure out how much potential energy the weights have to operate your clock:
$$P E=(2 \mathrm{~kg})\left(9.81 \mathrm{~m} / \mathrm{s}^2\right)(0.30 \mathrm{~m})=5.9 \mathrm{~J}$$
You can verify the units are correct in this equation by the equivalent energy unit equations I show earlier.

物理代写|热力学代写Thermodynamics代考|Internal energy

Internal energy is associated with both the motion and structure of molecules in a substance. Molecular or atomic movement by rotation, translation, and vibration in a substance increases as energy is added to the system. A change in kinetic energy of molecules often results in a temperature change of a substance. This form of internal energy is called sensible energy because it can be “sensed” by a thermometer. The symbol used for internal energy is $U$.
The molecular structure of a substance can change when energy is added to the system – for example, by melting or evaporating. Various forces bind molecules and atoms together in a substance. These binding forces are strongest in solids, which is why solids retain their shape. The binding forces are weaker in liquids, which stay together but change shape and fill containers. In gases, the binding forces are weakest; a gas freely expands until it fills a closed container. The following forms of internal energy interact with different kinds of binding forces:
$\sim$ Latent energy: When a substance changes phase (such as a solid melting into a liquid), some of the molecular binding force energy is overcome by thermal energy. The amount of energy required to break these bonds is called latent energy because thermal energy is added to the substance and its temperature doesn’t change during the phase-change process. A thermometer can’t sense the energy added during a phase change, so the energy is “hidden” or latent. See Chapter 3 for more details on phase changes. Latent energy is given different names for different kinds of phase changes:

• When a liquid freezes (or melts), the latent energy is called the latent heat of fusion ( $h_{\text {s }}$ ). The subscript “s” stands for the solid; the subscript “f” stands for the liquid.
• When a liquid evaporates (or condenses), it’s called the latent heat of vaporization $\left(h_i\right)$. The subscript “f” stands for the liquid; the subscript ” $g$ ” stands for the gas.
• When a solid evaporates directly to a gas (like dry ice does), it’s called the latent heat of sublimation ( $h_{\text {ss }}$ ). The subscript “s” stands for the solid; the subscript “g” stands for the gas.
$\sim$ Chemical energy: Chemical energy is used when fuels are burned in combustion reactions. When a fuel is burned, some chemical bonds are destroyed while new ones are formed. This can release energy stored in the molecular bonds of a combustible material. Chemical energy is present in every chemical reaction, but not all chemical reactions are of interest in thermodynamics. I discuss chemical energy related to common combustion processes in Chapter 16.

Nuclear energy: This type of energy is one of the strongest forms of molecular energy because it’s associated with the nucleus of an atom. This energy form isn’t discussed in thermodynamics at this level, but at least you know it exists.

物理代写|热力学代写Thermodynamics代考|Potential energy

$$P E=m \cdot g \cdot z$$

$$P E=(2 \mathrm{~kg})\left(9.81 \mathrm{~m} / \mathrm{s}^2\right)(0.30 \mathrm{~m})=5.9 \mathrm{~J}$$

物理代写|热力学代写Thermodynamics代考|Internal energy

$\sim$潜能:当物质变相时(如固体熔融成液体)，部分分子结合能被热能所克服。打破这些键所需的能量被称为潜能，因为热能被添加到物质中，而在相变过程中，物质的温度不会改变。温度计无法感知相变过程中增加的能量，因此能量是“隐藏的”或潜在的。有关相变的更多细节，请参见第3章。对于不同类型的相变，势能有不同的名称:

$\sim$化学能:当燃料在燃烧反应中燃烧时使用化学能。当燃料燃烧时，一些化学键被破坏，而新的化学键形成。这可以释放储存在可燃材料分子键中的能量。化学能存在于每一个化学反应中，但不是所有的化学反应都与热力学有关。我将在第16章讨论与常见燃烧过程有关的化学能。

MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。