ENGI 1313 Mechanics I
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ENGI 1313 Mechanics I . Lecture 07: Vector Dot Product. Chapter 2 Objectives. to review concepts from linear algebra to sum forces, determine force resultants and resolve force components for 2D vectors using Parallelogram Law to express force and position in Cartesian vector form
ENGI 1313 Mechanics I
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ENGI 1313 Mechanics I Lecture 07: Vector Dot Product
Chapter 2 Objectives • to review concepts from linear algebra • to sum forces, determine force resultants and resolve force components for 2D vectors using Parallelogram Law • to express force and position in Cartesian vector form • to examine the concept of dot product
Lecture 07 Objectives • to examine the concept of dot product
Overview of Dot Product • Definition • Laws of Operations • Commutative law • Scalar Multiplication • Distributive law
Overview of Dot Product (cont.) • Dot Product of Cartesian Vectors Go to zero
Application of Dot Product • Angle between two vectors • Cables forces and the pole? • • and ? Component magnitudes
If A||has + sense then same direction as u ^ Application of Dot Product (cont.) • Component magnitudeof A on a parallel or collinear linewith line aa • Recall Component A||
Application of Dot Product (cont.) • The vector A|| canbe determined by: Vector A|| Application of Dot Product for Component A|| Multiply by Unit Vector ûto obtain Vector A||
Application of Dot Product (cont.) • For force vector F at Point A: What is the component magnitudeparallel (|F1|) to the pipe (OA)?
Application of Dot Product (cont.) • For force vector F at Point A: what is the component magnitudeperpendicular (F2) to the pipe (OA)? • Method 1 • Method 2
Comprehension Quiz 7-01 • The dot product of two vectors results in a _________ quantity. • A) scalar • B) vector • C) complex number • D) unit vector • Answer: A
A Example Problem 7-01 • For the Cartesian force vector, find the angle between the force vector and the pole, and the magnitude of the projection of the force along the pole OA
A Example Problem 7-01 (cont.) • Position vector rOA • Magnitude of |rOA| • Magnitude of |F|
A Example Problem 7-01 (cont.) • Find the angle between rOA and F
A Example Problem 7-01 (cont.) • Find magnitude of the projection of the force F along the pole OA
Comprehension Quiz 7-02 • If the dot product of two non-zero vectors is 0, then the two vectors must be ______ to each other. • A) parallel (pointing in the same direction) • B) parallel (pointing in the opposite direction) • C) perpendicular • D) cannot be determined. • Answer: C
Comprehension Quiz 7-03 • The Dot product can be used to find all of the following except ____ • A) sum of two vectors • B) angle between two vectors • C) vector component parallel to a line • D) vector component perpendicular to a line • Answer: A
Comprehension Quiz 7-04 • Find the dot product (PQ) for • A) -12 m • B) 12 m • C) 12 m2 • D) -12 m2 • E) 10 m2 • Answer: C
Classification of Textbook Problems Hibbeler (2007)
References • Hibbeler (2007) • http://wps.prenhall.com/esm_hibbeler_engmech_1