184_notes:defining_a_system

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184_notes:defining_a_system [2017/08/21 02:43] – [Defining A System] pwirving184_notes:defining_a_system [2020/08/24 19:30] (current) – dmcpadden
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 ~~NOTOC~~ ~~NOTOC~~
 +/*[[184_notes:three_principles|Next Page: 3 Fundamental Principles of Mechanics]]
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 +[[184_notes:math_review|Previous Page: Math Review]]*/
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 ===== Defining A System ===== ===== Defining A System =====
  
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 ==== Lecture Video ==== ==== Lecture Video ====
  
-{{youtube>FuTw1sc6bL4?large}}+{{youtube>SdATPEWh2B8?large}}
  
 ==== The System ==== ==== The System ====
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 The system is the object or the collection of objects that you are interested in (usually to describe its motion, explain why it follows some path, etc.). A system has various physical quantities associated with it: mass, energy, momentum, angular momentum, and entropy. These quantities can change for a system by interacting with the surroundings.  The system is the object or the collection of objects that you are interested in (usually to describe its motion, explain why it follows some path, etc.). A system has various physical quantities associated with it: mass, energy, momentum, angular momentum, and entropy. These quantities can change for a system by interacting with the surroundings. 
  
-In mechanics, you often picked the object that is in motion as your system because you are primarily interested in describing that motion or how that motion is changing. Your job in mechanics was to predict or explain the motion of objects. In E&M, the choice of system can be a bit more nuanced. You are still interested in choosing a system that helps you predict or explain something about the system, but what that something is can be motion, energy, or something altogether new - like [[184_notes:pc_efield|a field]] or [[184_notes:circuits|circuit]].+In mechanics, it was common to pick the object that is in motion as your system because you are primarily interested in describing that motion or how that motion is changing. Your job in mechanics was to predict or explain the motion of objects. In E&M, the choice of system can be a bit more nuanced. You are still interested in choosing a system that helps you predict or explain something about the system, but what that something is can be motion, energy, or something altogether new - like [[184_notes:pc_efield|a field]] or circuit.
  
 When we refer to a quantity as "internal," we are referring to something that is //inside// the system we chose. When we refer to a quantity as "internal," we are referring to something that is //inside// the system we chose.
  
-{{ 184_notes:syssurr.png?250}}+[{{ 184_notes:syssurr.png?250|This figure shows a system and its physical quantities (charge (q), mass, momentum (p), etc.) as well as the ways the surroundings can influence the system (force, heat, torque, etc.).}}]
  
 ==== The Surroundings ==== ==== The Surroundings ====
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