3.3 Vector Addition and Subtraction: Analytical Methods

3 min readjune 18, 2024

Vector addition and subtraction are key skills in physics. These methods allow us to combine or compare quantities with both and direction, like forces or velocities. Understanding how to break vectors into and recombine them is crucial for solving many physics problems.

The notes cover analytical and graphical methods for vector operations. They explain how to find vector components, add or subtract vectors, and determine the characteristics of resultant vectors. These techniques are essential for analyzing complex systems and predicting outcomes in physics scenarios.

Vector Addition and Subtraction

Principles of vector addition

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  • Vectors possess both magnitude and direction represented by arrows, with the length indicating magnitude and the arrowhead pointing in the direction of the vector (, )
  • Vector addition and subtraction can be performed analytically using the breaks vectors into their horizontal (x) and vertical (y) components
  • Components are added or subtracted separately, then combined to find the (, )
  • To add vectors analytically:
    1. Add the x-components of all vectors to find the resultant
    2. Add the y-components of all vectors to find the resultant
    3. Combine the resultant x and y components to determine the magnitude and direction of the (, )
  • To subtract vectors analytically:
    1. Subtract the x-component of the second vector from the x-component of the first vector
    2. Subtract the y-component of the second vector from the y-component of the first vector
    3. Combine the resultant x and y components to determine the magnitude and direction of the resultant vector (, )
  • The is a graphical technique for vector addition, where vectors are arranged to form a parallelogram and the diagonal represents the sum

Analytical vector components

  • To find the horizontal (x) component of a vector multiply the magnitude of the vector by the of the angle it makes with the positive x-axis , where AA is the magnitude of the vector and θ\theta is the angle ()
  • To find the vertical (y) component of a vector multiply the magnitude of the vector by the of the angle it makes with the positive x-axis , where AA is the magnitude of the vector and θ\theta is the angle ()
  • The angle θ\theta is measured counterclockwise from the positive x-axis to the vector
  • If the vector is in the second pointing up and to the left, the x-component will be negative (northwest wind)
  • If the vector is in the fourth quadrant pointing down and to the right, the y-component will be negative (southeast acceleration)
  • involves breaking a vector into perpendicular components, typically along the x and y axes

Resultant vector characteristics

  • To find the magnitude of the resultant vector use the to calculate the magnitude from the resultant x and y components , where RR is the magnitude of the resultant vector, RxR_x is the resultant x-component, and RyR_y is the resultant y-component (total from origin)
  • To find the direction of the resultant vector calculate the angle θ\theta that the resultant vector makes with the positive x-axis using the θ=tan1(RyRx)\theta = \tan^{-1} (\frac{R_y}{R_x}), where RyR_y is the resultant y-component and RxR_x is the resultant x-component
  • The angle θ\theta will be in the quadrant determined by the signs of the resultant x and y components
    1. First quadrant with both positive: 0°θ<90°0° \leq \theta < 90° (northeast resultant force)
    2. Second quadrant with x negative, y positive: 90°θ<180°90° \leq \theta < 180° (northwest resultant velocity)
    3. Third quadrant with both negative: 180°θ<270°180° \leq \theta < 270° (southwest net acceleration)
    4. Fourth quadrant with x positive, y negative: 270°θ<360°270° \leq \theta < 360° (southeast total displacement)

Vector and Scalar Quantities

  • A vector is a quantity with both magnitude and direction, existing in a
  • A is a quantity with only magnitude, such as temperature or mass
  • Unit vectors are vectors with a magnitude of 1, often used to indicate direction in a coordinate system

Key Terms to Review (44)

: The arrow symbol (→) is a mathematical notation used to represent vector addition and subtraction in analytical methods. It indicates the direction and magnitude of a vector quantity, serving as a visual aid in understanding and manipulating vector operations.
$\theta = \tan^{-1} \left(\frac{R_y}{R_x}\right)$: The term $\theta = \tan^{-1} \left(\frac{R_y}{R_x}\right)$ represents the angle between a vector and the positive x-axis in a two-dimensional coordinate system. It is a fundamental concept in the analytical methods of vector addition and subtraction, allowing for the determination of the direction of a resultant vector based on its x and y components.
$A_x = A \cos \theta$: $A_x = A \cos \theta$ is a fundamental equation in vector analysis that describes the x-component of a vector $\vec{A}$ in terms of the magnitude of the vector $A$ and the angle $\theta$ between the vector and the x-axis. This equation is particularly important in the context of vector addition and subtraction using analytical methods.
$A_y = A \sin \theta$: $A_y = A \sin \theta$ is an equation that describes the vertical component of a vector $\vec{A}$ in a two-dimensional coordinate system. The vertical component, $A_y$, is equal to the magnitude of the vector, $A$, multiplied by the sine of the angle, $\theta$, between the vector and the positive x-axis. This equation is particularly useful in the context of vector addition and subtraction using analytical methods.
$R = \sqrt{R_x^2 + R_y^2}$: $R = \sqrt{R_x^2 + R_y^2}$ is a mathematical expression that represents the magnitude or length of a vector in a two-dimensional coordinate system. It is used to calculate the resultant vector from the vector components $R_x$ and $R_y$, which are the projections of the vector along the $x$ and $y$ axes, respectively.
Analytical methods: Analytical methods involve using mathematical techniques to solve problems related to vector addition and subtraction. These methods typically use trigonometry and algebra to find the magnitude and direction of resultant vectors.
Cartesian Coordinates: Cartesian coordinates are a system used to locate points in a two-dimensional or three-dimensional space. This system uses perpendicular axes, known as the x-axis and y-axis in two dimensions, or the x-axis, y-axis, and z-axis in three dimensions, to uniquely identify the position of a point.
Commutative Property: The commutative property is a fundamental principle that states the order in which two or more quantities are combined does not affect the final result. This property is particularly important in the context of vector addition and subtraction, where the order in which vectors are combined does not change the resulting vector.
Component Method: The component method is a technique used in vector addition and subtraction to break down vectors into their individual components, analyze them separately, and then recombine them to find the resultant vector. This method allows for a systematic and analytical approach to working with vectors.
Components: Components refer to the individual parts or elements that make up a larger system or object. In the context of vector addition and subtraction, components are the individual vectors that can be combined or separated to represent a resultant vector.
Cosine: Cosine is a trigonometric function that represents the ratio of the adjacent side to the hypotenuse of a right triangle. It is one of the fundamental trigonometric functions used in various applications, including vector analysis and the calculation of work done by a force.
Displacement: Displacement is a vector quantity that refers to the change in position of an object. It has both magnitude and direction, indicating how far and in what direction the object has moved from its initial position.
Displacement: Displacement is the change in position of an object, measured from a reference point or origin. It describes the straight-line distance and direction an object has moved, without regard to the path taken.
Distributive Property: The distributive property is a fundamental mathematical concept that allows for the simplification of expressions involving multiplication and addition or subtraction. It states that the product of a number and a sum is equal to the sum of the products of the number with each addend.
Eastward Component of Velocity: The eastward component of velocity refers to the portion of an object's total velocity that is directed towards the east. This is an important concept in the context of vector addition and subtraction, as it allows for the decomposition of a velocity vector into its directional components.
Inverse Tangent Function: The inverse tangent function, also known as the arctangent function, is a trigonometric function that calculates the angle whose tangent is a given value. It is the inverse of the tangent function, allowing one to find the angle given the tangent ratio.
Magnitude: Magnitude is a measure of the size or scale of a quantity, representing its absolute or relative value. It is a fundamental concept in physics, particularly in the context of vectors, forces, and displacement.
Meters per Second: Meters per second (m/s) is a unit of measurement that quantifies the rate of change in an object's position over time. It is commonly used to express the speed or velocity of an object in the context of physics and various other scientific disciplines.
Net Acceleration: Net acceleration refers to the combined or resultant acceleration experienced by an object when multiple forces are acting upon it. It is the vector sum of all the accelerations acting on the object, determined by the application of Newton's second law of motion.
Net Force: Net force is the vector sum of all the individual forces acting on an object. It represents the overall force that determines the object's acceleration or lack thereof, in accordance with Newton's laws of motion.
Newtons: Newtons are the fundamental unit of force in the International System of Units (SI). They are used to measure the strength or intensity of a push or pull on an object, and are essential in understanding the concept of force and its applications in physics.
Northward Component of Force: The northward component of a force is the portion of the force that is directed in the northward direction. This concept is particularly relevant in the context of vector addition and subtraction, where forces can be broken down into their horizontal and vertical components to facilitate calculations and analysis.
Orthogonal Decomposition: Orthogonal decomposition is a mathematical concept that involves breaking down a vector into mutually perpendicular components. This technique is particularly useful in the context of vector addition and subtraction, as it allows for the analytical analysis of vector operations.
Parallelogram Method: The parallelogram method is a graphical technique used to add or subtract vectors by representing them as the sides of a parallelogram. It allows for the determination of the resultant vector's magnitude and direction through the construction of a parallelogram.
Polar Coordinates: Polar coordinates are a two-dimensional coordinate system that uses the distance from a reference point, called the pole, and the angle from a reference direction, called the polar axis, to locate a point on a plane. This system provides an alternative to the more commonly used Cartesian coordinate system.
Pythagorean Theorem: The Pythagorean Theorem is a fundamental relationship in geometry that describes the connection between the lengths of the sides of a right triangle. It states that the square of the length of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the lengths of the other two sides.
Quadrant: A quadrant is one of the four equal divisions of a circle or a coordinate plane, typically used to represent the relative position of objects or values. It is a fundamental concept in vector addition and subtraction, as it helps to visualize and analyze the direction and magnitude of vectors.
Relative Velocity: Relative velocity is the velocity of an object as observed from the perspective of another object or frame of reference. It describes the motion of one object relative to another, rather than the absolute motion of an object in a fixed coordinate system.
Resolution of Vectors: The resolution of vectors is the process of breaking down a vector into its component parts along different axes or directions. This is a crucial concept in the analytical methods of vector addition and subtraction, as it allows for the manipulation and calculation of vector quantities.
Resultant Force: The resultant force is the single force that represents the combined effect of two or more individual forces acting on an object. It is the vector sum of all the forces acting on an object, and it determines the object's acceleration and the direction of its motion.
Resultant vector: A resultant vector is the single vector that has the same effect as two or more vectors added together. It represents the combined magnitude and direction of these vectors.
Resultant Vector: The resultant vector is the single vector that represents the combined effect of two or more vectors acting on an object. It is the vector sum of all the individual vectors, capturing the net displacement, force, or quantity being measured.
Scalar: A scalar is a physical quantity that has only magnitude and no direction. Examples include mass, temperature, and electric potential.
Scalar: A scalar is a physical quantity that has only a magnitude, or numerical value, and no direction. Scalars are contrasted with vectors, which have both a magnitude and a direction. Scalars are commonly used in physics to describe various physical properties and quantities.
Sine: Sine is a trigonometric function that represents the ratio of the length of the opposite side to the length of the hypotenuse of a right-angled triangle. It is one of the fundamental functions used in the study of vectors and their analytical methods.
Tangent: A tangent is a line that touches a curve at a single point, forming a 90-degree angle with the curve at that point. It is a fundamental concept in vector addition and subtraction, as it allows for the decomposition of vectors into perpendicular components.
Total Displacement: Total displacement refers to the overall change in position of an object from its initial to its final location. It is a vector quantity, meaning it has both magnitude and direction, and is the most direct path between the start and end points of an object's motion.
Total Velocity: Total velocity is the vector sum of all the velocities acting on an object. It represents the net velocity, or the overall speed and direction of an object's motion, taking into account the combined effect of multiple velocities.
Unit Vector: A unit vector is a dimensionless vector with a magnitude of 1 that points in a specific direction. It is used to represent the direction of a vector without considering its magnitude.
Vector Space: A vector space is a mathematical structure that consists of a set of elements called vectors, which can be added together and multiplied by numbers, called scalars, to produce new vectors. Vector spaces are fundamental in many areas of mathematics and physics, including linear algebra, calculus, and quantum mechanics.
Vector Subtraction: Vector subtraction is the process of finding the difference between two vectors by subtracting their corresponding components. It is a fundamental operation in vector mathematics that allows for the manipulation and analysis of vector quantities, which are essential in various fields of physics, engineering, and mathematics.
Velocity: Velocity is a vector quantity that describes the rate of change in the position of an object over time. It includes both the speed of the object and the direction of its motion. Velocity is a crucial concept in understanding the motion of objects and the fundamental principles of physics.
X-Component: The x-component of a vector is the projection or portion of the vector along the x-axis. It represents the horizontal or left-right direction of the vector and is a crucial component in vector addition and subtraction using analytical methods.
Y-component: The y-component of a vector is the vertical or up-down portion of the vector's magnitude. It represents the component of the vector that is directed along the y-axis of a coordinate system. The y-component is a crucial factor in vector addition and subtraction, as it allows for the decomposition of a vector into its perpendicular parts.
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