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Lesson 2: Physics 150 / 215 2-D Motion. Coordinate Systems Vectors in general Special Vectors. Coordinate Systems. 1. Fix a reference point : ORIGIN 2. Define a set of directed lines that intersect at origin: COORDINATE AXES
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Lesson 2: Physics 150 / 2152-D Motion • Coordinate Systems • Vectors in general • Special Vectors
Coordinate Systems 1. Fix a reference point : ORIGIN 2. Define a set of directed lines that intersect at origin: COORDINATE AXES 3. Instructions on how to label point with respect origin and axes. COORDINATES
y p b r x a • rectangular Cartesian coordinates of point • p=(a,b) • plane polar coordinates of point • p = (r,)
Two vectors are equal if they have • same length • same direction = parallel transport is moving vector without changing length or direction
V2 Addition tip + V1 tail
V1 V2 V1 + V2 V2
V j i V Vx Vx j i Vy Cos V Vx Vy V Sin
can always represent a vector by a directed line segment: y x • Two vectors are equal if they have • same length • same direction =
Vector Addition is Commutative : a + b = b + a Associative : a + ( b + c ) = ( a + b ) + c - a = vector that has same length as a but opposite direction Multiplication by scalar : ì m > 0 vector in same direction as a ï ï but m times as long m a = í m < 0 vector in opposite direction as a ï ï î but m times as long
Solving Problems Involving Vectors 1. Graphically ! Draw all vectors in pencil ! Arrange them tip to tail ! Draw a vector from the tail of the first vector to the tip of the last one.
! measure the angle the vector makes with the positive x-axis ! measure the length of the vector. ! measure the length of its X component ! measure the length of its Y component
2. Algebraically ! write all vectors in terms of their X and Y components ! The X component of the sum of the vectors is the sum of the X components ! The Y component of the sum of the vectors is the sum of the Y components
coordinates of vectors (x,y) V yj xi V=xi + yj
1-1 correspondence between vectors and their coordinates V = xi + yj (x,y)
Special Vectors (x,y) r d ri rf
special unit vectors k i j