rev.s08 mac 1114 module 9 introduction to vectors

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MAC 1114

Module 9

Introduction to Vectors

2Rev.S08

Learning ObjectivesUpon completing this module, you should be able to:

1. Learn and apply basic concepts about vectors.

2. Perform operations on vectors.

3. Represent a vector quantity algebraically and find unit vectors.

4. Compute dot products and the angle between two vectors.

5. Use vectors to solve applications.

http://faculty.valenciacc.edu/ashaw/ Click link to download other modules.

http://faculty.valenciacc.edu/ashaw/

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Introduction to Vectors


- Introduction to Vectors, Operations, and - Introduction to Vectors, Operations, and the Dot Productsthe Dot Products

- Application of Vectors- Application of Vectors

There are two major topics in this module:


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Quick Review on Parallel Lines and Transversal


Parallel lines are lines that lie in the same plane and do not intersect.

When a line q intersects two parallel lines, q, is called a transversal.

m

n

parallel lines

qTransversal


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Important Angle Relationships


Angle measures are equal.2 & 6, 1 & 5, 3 & 7, 4 & 8

Corresponding angles

Angle measures add to 180.4 and 6

3 and 5

Interior angles on the same side of the transversal

Angle measures are equal.1 and 8

2 and 7

Alternate exterior angles

Angles measures are equal.4 and 5

3 and 6

Alternate interior angles

RuleAnglesName

m

n

q


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Basic Terminology


A vector in the plane is a directed line segment. Consider vector AB

A is called the initial point B is called the terminal point

Magnitude: length of a vector, expressed as The sum of two vectors is also a vector. The vector sum A + B is called the resultant.


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Basic Terminology Continued


A vector with its initial point at the origin is called a position vector.

A position vector u with its endpoint at the point (a, b) is written

The numbers a and b are the horizontal component and vertical component of vector u.

The positive angle between the x-axis and a position vector is the direction angle for the vector.


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What are Magnitude and Direction Angle of Vector ?


The magnitude (length) of vector u = is given by

The direction angle θ satisfies where a ≠ 0.


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Example of Finding Magnitude and Direction Angle


Find the magnitude and direction angle for

Magnitude:

Direction Angle:

Vector u has a positive horizontal component.

Vector u has a negative vertical component, placing the vector in quadrant IV.


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What are the Horizontal and Vertical Components?


The horizontal and vertical components, respectively, of a vector u having magnitude |u| and direction angle θ are given by

That is,


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Example of Finding the Horizontal and Vertical Components


Vector w has magnitude 35.0 and direction angle 51.2. Find the horizontal and vertical components.

Therefore, w = The horizontal component is 21.9, and the vertical

component is 27.3.


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Example


Write each vector in the Figure on the right in the form

u = 5cos60o,5sin60o


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Solutions



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What are Vector Operations?


For any real numbers a, b, c, d, and k,


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Example: Vector Operations


a) 4v

b) 2u + v

c) 2u − 3v

u = 4,10

v = 5,−3Let and find:


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How to Compute Dot Product?


A unit vector is a vector that has magnitude 1.

Dot Product

The dot product of two vectors

is denoted u • v, read “u dot v,” and given by


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Example of Finding Dot Products


Find each dot product.


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What are the Properties of the Dot Product?


For all vectors u, v, and w and real numbers k, a) b) c) d) e) f)

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What is the Geometric Interpretation of Dot Product?


If θ is the angle between the two nonzero vectors u and v, where 0≤ θ ≤ 180, then

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Example of Finding the Angle Between the Two Vectors


Find the angle θ between two vectors

By the geometric

cosθ =u⋅vu v

=5,6 ⋅ 3,4

5,6 3,4

=5(3) +6(4)

25+36 9+16

=39

5 61≈.9986876635

θ ≈cos−1 .9986876635≈2.94o

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Example


Forces of 10 newtons and 50 newtons act on an object at right angles to each other. Find the magnitude of the resultant and the angle of the resultant makes with the larger force.

The resultant vector, v, has magnitude 51 and make an angle of 11.3 with the larger force.

10

50

10

θ

v

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Example


A vector w has a magnitude of 45 and rests on an incline of 20. Resolve the vector into its horizontal and vertical components.

The horizontal component is 42.3 and the vertical component is 15.4.

v

u

45

20

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Example


A ship leaves port on a bearing of 28.0 and travels 8.20 mi. The ship then turns due east and travels 4.30 mi. How far is the ship from port? What is its bearing from port?

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Example Continued


Vectors PA and AE represent the ship’s path. Magnitude and bearing:

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Example Continued


The ship is about 10.9 mi from port. To find the bearing of the ship from port, find

angle APE.

Add 20.4 to 28.0 to find that the bearing is 48.4.

10.9

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We have learned how to find the resultant of two vectors.

A vector that will counterbalance the resultant is called the equilibrant. For instance, the equilibrant of vector u is the vector -u.

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What is the Equilibrant?


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What have we learned?

We have learned to:

1. Learn and apply basic concepts about vectors.

2. Perform operations on vectors.

3. Represent a vector quantity algebraically and find unit vectors.

4. Compute dot products and the angle between two vectors.

5. Use vectors to solve applications.


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Credit

Some of these slides have been adapted/modified in part/whole from the slides of the following textbook:

• Margaret L. Lial, John Hornsby, David I. Schneider, Trigonometry, 8th Edition


rev.s08 mac 1114 module 9 introduction to vectors

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