183_notes:scalars_and_vectors

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183_notes:scalars_and_vectors [2021/01/23 21:55] – [Definitions & Diagrams] stumptyl183_notes:scalars_and_vectors [2024/01/30 13:50] (current) – [Vector Simulation] hallstein
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 ===== Scalars and Vectors ===== ===== Scalars and Vectors =====
  
-We often use mathematics to describe physical situations. Two types of quantities that are particularly important for describing physical systems are scalars and vectors. In the notes below, you will read about those quantities (in general) and their properties.+We often use mathematics to describe physical situations. Two types of quantities that are particularly important for describing physical systems are scalars and vectors. **In the notes below, you will read about those quantities (in general) and their properties.**
 ==== Lecture Video ==== ==== Lecture Video ====
  
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 ==== Definitions & Diagrams ==== ==== Definitions & Diagrams ====
  
-//'''Scalars''' are quantities that can be represented by a single number. Typical examples include mass, volume, density, and speed.//+//**Scalars** are quantities that can be represented by a single number. Typical examples include mass, volume, density, and speed.//
  
-{{ course_planning:course_notes:basic_vector.png?200| }}+{{ basic_vector_new.png?300| }}
  
-//'''Vectors''' are quantities that have both a magnitude and direction. Typical examples include displacement, velocity, momentum, and force.//+//**Vectors** are quantities that have both a magnitude and direction. Typical examples include displacement, velocity, momentum, and force.//
  
 Vectors are often represented with arrows. The end with the triangle is the "tip" or "head." The other end is called the "tail." The tail of a vector can be located anywhere; it is the difference between the tip and the tail that defines the vector itself. To the right is an example of a typical representation (a diagram) of a vector with the tip and tail labeled. We have no such diagrammatic representations for scalars. Vectors are often represented with arrows. The end with the triangle is the "tip" or "head." The other end is called the "tail." The tail of a vector can be located anywhere; it is the difference between the tip and the tail that defines the vector itself. To the right is an example of a typical representation (a diagram) of a vector with the tip and tail labeled. We have no such diagrammatic representations for scalars.
-==== Defining Vectors Mathematically ====+===== Defining Vectors Mathematically =====
  
-{{ course_planning:course_notes:3d_vector.png?300| A position vector defined in 3D space}}+{{ course_planning:course_notes:scalars_vectors_new.png?300| A position vector defined in 3D space}}
 We define vectors in three dimensional space relative to some origin (where the tail of the vector is located). For example, a position vector →r might defined relative to the origin of coordinates. The measures of the vector along the coordinate axes are called the vector's "components," which can be positive or negative. Mathematically, a vector can be written with "bracket" notation: We define vectors in three dimensional space relative to some origin (where the tail of the vector is located). For example, a position vector →r might defined relative to the origin of coordinates. The measures of the vector along the coordinate axes are called the vector's "components," which can be positive or negative. Mathematically, a vector can be written with "bracket" notation:
  
-r=→r=⟨rx,ry,rz⟩
+r=→r=⟨rx,ry,rz⟩
 
  
-where rx, ry, and rz are the vector components in the x, y, and z direction respectively. They tell you "how much" of the vector →r is aligned with each coordinate direction. The vector itself is denoted either in bold face (in texts) or with an arrow above it (both texts and handwritten).+//where rx, ry, and rz are the vector components in the x, y, and z direction respectively.// They tell you "how much" of the vector →r is aligned with each coordinate direction. The vector itself is denoted either in bold face (in texts) or with an arrow above it (both texts and handwritten).
  
 In physics, we often use the symbol →r to represent the position vector, that is, the location of an object with respect to another point (e.g., the origin of coordinates). In physics, we often use the symbol →r to represent the position vector, that is, the location of an object with respect to another point (e.g., the origin of coordinates).
  
-=== Length of a vector ===+\\ 
 +==== Length of a vector ====
  
-The magnitude (or length) of a vector is a scalar quantity. Mathematically, we represent the magnitude of a vector like this:+The **magnitude** (or length) of a vector is a scalar quantity. Mathematically, we represent the magnitude of a vector like this:
  
 r=|→r|=√r2x+r2y+r2z
 r=|→r|=√r2x+r2y+r2z
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 This calculation simply uses the [[https://en.wikipedia.org/wiki/Pythagorean_theorem|Pythagorean theorem]] in three dimensions to determine this length. This calculation simply uses the [[https://en.wikipedia.org/wiki/Pythagorean_theorem|Pythagorean theorem]] in three dimensions to determine this length.
  
-=== Unit vector ===+\\ 
 +==== Unit vector ====
  
-Any vector can be multiplied or divided by a scalar quantity. Often it is useful to divide a vector by its own magnitude. The result is the "unit vector." The unit vector is a vector with length 1, but that points in the direction of the original vector. The unit vector has no units (e.g., the unit vector of a position vector with units of meters has no units itself). Mathematically, we represent the unit vector like this:+Any vector can be multiplied or divided by a scalar quantity. Often it is useful to divide a vector by its own magnitude. The result is the "unit vector." **The unit vector** is a vector with length 1, but that points in the direction of the original vector. //The unit vector has no units// (e.g., the unit vector of a position vector with units of meters has no units itself). Mathematically, we represent the unit vector like this:
  
 ˆr=→r|→r|=⟨rx,ry,rz⟩√r2x+r2y+r2z
 ˆr=→r|→r|=⟨rx,ry,rz⟩√r2x+r2y+r2z
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 ==== Determining Vector Components in Two Dimensions ==== ==== Determining Vector Components in Two Dimensions ====
  
-[{{ course_planning:course_notes:2d_vector.png?250|2D vector decomposition into components}}]+[{{ 183_notes:2d_vector_new.png?250|2D vector decomposition into components}}]
  
 Two dimensional vectors are easy to sketch, so often we will use them when describing different physical systems and problems. For these vectors, it is often useful to define an angle (θ) between the vector and one of the coordinate directions (see the figure to the right). The typical relationship between the x and y components of a 2D vector and its magnitude and this angle (when defined from the positive x-axis) is: Two dimensional vectors are easy to sketch, so often we will use them when describing different physical systems and problems. For these vectors, it is often useful to define an angle (θ) between the vector and one of the coordinate directions (see the figure to the right). The typical relationship between the x and y components of a 2D vector and its magnitude and this angle (when defined from the positive x-axis) is:
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 ry=|→r|sinθ
 ry=|→r|sinθ
  
-**The above equations only work when the vectors are decomposed with along the x and y axis as defined in the figure to the right.** Oftentimes, an angle that is given or derived cannot make use of the simple decomposition formulae above. The geometric properties of the problem will dictate which trigonometric functions are used.+//The above equations only work when the vectors are decomposed with along the x and y axis as defined in the figure to the right.// Oftentimes, an angle that is given or derived cannot make use of the simple decomposition formulae above. The geometric properties of the problem will dictate which trigonometric functions are used. 
 + 
 +{{youtube>WwxevEMyxFk?large}}
 ==== Adding & Subtracting Vectors ===== ==== Adding & Subtracting Vectors =====
  
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 →a−→b=⟨ax,ay,az⟩−⟨bx,by,bz⟩=⟨ax−bx,ay−by,az−bz⟩
 →a−→b=⟨ax,ay,az⟩−⟨bx,by,bz⟩=⟨ax−bx,ay−by,az−bz⟩
  
-{{ course_planning:course_notes:2d_vector_addition.png?250|graphical vector addition}}+{{ 183_notes:vector_addition_new.png?250|graphical vector addition}}
 Graphically, vector addition and subtraction use the "tip-to-tail" method.  Graphically, vector addition and subtraction use the "tip-to-tail" method. 
  
 **Vector addition** For addition, place the tail of the second vector at the tip of the first vector. The vector that points from the tail of the first to the tip of the second is the sum or the "resultant" vector. The image to the right demonstrates this for two vectors, →a and →b. **Vector addition** For addition, place the tail of the second vector at the tip of the first vector. The vector that points from the tail of the first to the tip of the second is the sum or the "resultant" vector. The image to the right demonstrates this for two vectors, →a and →b.
  
-{{ course_planning:course_notes:2d_vector_subtraction.png?225|graphical vector subtraction}}+{{ 183_notes:vector_subtraction_new.png?225|graphical vector subtraction}}
 **Vector subtraction** For subtraction, draw the vector that points directly opposite of the second vector. Place the tail of this reversed second vector at the tip of the first vector. The vector that points from the tail of the first to the tip of the reversed second is the difference vector. The image to the right demonstrates this for two vectors, →a and →b. **Vector subtraction** For subtraction, draw the vector that points directly opposite of the second vector. Place the tail of this reversed second vector at the tip of the first vector. The vector that points from the tail of the first to the tip of the reversed second is the difference vector. The image to the right demonstrates this for two vectors, →a and →b.
  
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 Here's simulation that let's you play with vectors in 2D.((Credit the [[http://phet.colorado.edu|PhET Team]] at the University of Colorado for the simulation.)) If the embedded simulation doesn't work, you can find it [[http://phet.colorado.edu/sims/vector-addition/vector-addition_en.html|on the PhET website]]. Here's simulation that let's you play with vectors in 2D.((Credit the [[http://phet.colorado.edu|PhET Team]] at the University of Colorado for the simulation.)) If the embedded simulation doesn't work, you can find it [[http://phet.colorado.edu/sims/vector-addition/vector-addition_en.html|on the PhET website]].
  
-{{url>http://phet.colorado.edu/sims/vector-addition/vector-addition_en.html 800px,600px | PhET Vector Simulation}}+{{url>https://phet.colorado.edu/sims/html/vector-addition/latest/vector-addition_all.html 800px,600px | PhET Vector Simulation}}
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