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--- 184_notes:three_principles [2017/06/05 15:00] – [The Three Fundamental Principles of Mechanics] caballero
+++ 184_notes:three_principles [2020/08/24 19:31] (current) – dmcpadden
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 ~~NOTOC~~
+/*[[184_notes:using_python|Next Page: Using Python]]
+[[184_notes:defining_a_system|Previous Page: Defining a System]]*/
 ===== The Three Fundamental Principles of Mechanics =====
-In your mechanics, you learned about the three fundamental principles (though they may have been called by different names): [[183_notes:momentum_principle|the momentum principle]], [[183_notes:define_energy#the_first_law_of_thermodynamics_the_energy_principle|the energy principle]], and [[183_notes:l_principle|the angular momentum principle]]. It turns out these principles are central to the study of physics broadly, not simply mechanics; they are [[183_notes:fundamental_principles|deep truths about our universe]], which seem to hold in every observation we make and experiment we conduct.
+A major focus of introductory mechanics is understanding three fundamental principles of how objects interact (though they may have been called by different names): [[183_notes:momentum_principle|the momentum principle]], [[183_notes:define_energy#the_first_law_of_thermodynamics_the_energy_principle|the energy principle]], and [[183_notes:l_principle|the angular momentum principle]]. These principles are central to the study of physics broadly, not simply mechanics; they are [[183_notes:fundamental_principles|deep truths about our universe]], which seem to hold in every observation we make and experiment we conduct.
+As such, in Electricity & Magnetism (E&M for short), these fundamental principles do not change - we will still use these three principles.  In addition, this semester we will add another deep principle [[https://en.wikipedia.org/wiki/Charge_conservation|(conservation of charge)]] and talk about two new types of interactions: the electric interaction and the magnetic interaction. As we talk about these new interactions and this new principle, we will be relying on the three fundamental principles to talk about how a system responds, so it is worth reviewing these principles and how they work.
+==== Lecture Video ====
-As such, in Electricity & Magnetism (E&M for short), these fundamental principles do not change (and, indeed, we still apply them).  Instead, we focus on two new types of interactions: the electric interaction and the magnetic interaction and add to them another deep principle: [[https://en.wikipedia.org/wiki/Charge_conservation|conservation of charge]]. As we talk about these new interactions and this new principle, we will be relying on the three fundamental principles to talk about how a system responds, so it is worth reviewing these principles and how they work.
+{{youtube>FuTw1sc6bL4?large}}
 ==== The Momentum Principle ====
-[[183_notes:momentum_principle|The momentum principle]] describes how the momentum of a system will change as a result of external forces. Since momentum is a vector, this principle is really a set of three equations - one for each dimension. Therefore, it is also able to describe how an system will move in three dimensions. The momentum principle is the underlying theory behind [[https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion|Newton's Laws]] and the [[https://en.wikipedia.org/wiki/Equations_of_motion#Constant_translational_acceleration_in_a_straight_line|kinematic equations of motion]].
+[[183_notes:momentum_principle|The momentum principle]] describes how the momentum of a system will change as a result of external forces. Since momentum is a vector, this principle is really a set of three equations - one for momentum in the x-direction, one for momentum in the y-direction, and one for momentum in the z-direction. Therefore, it is also able to describe how an system will move in three dimensions. The momentum principle is the underlying theory behind [[https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion|Newton's Laws]] and the [[https://en.wikipedia.org/wiki/Equations_of_motion#Constant_translational_acceleration_in_a_straight_line|kinematic equations of motion]].
 $$\Delta \vec{p}_{sys} = \vec{F}_{ext} \Delta t$$