Starter If the height is 10m and the angle is 30 degrees, how long is the shadow? h/s = tan , so s...
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Transcript of Starter If the height is 10m and the angle is 30 degrees, how long is the shadow? h/s = tan , so s...
StarterIf the height is 10m and the angle is 30 degrees, how long is the shadow?
h/s = tanq, so s =h/tanq = 10/tan30 = 17.3m
Vectors and Vector Addition
1. Characteristics of Vectors2. Multiplying a vector by a scalar3. Adding Vectors Graphically4. Adding Vectors using
Components
What is a vector?
A vector is a mathematical quantity with two characteristics:
1. Magnitude or Length
2. Direction ( usually an angle)
Vectors vs. Scalars
A vector has a magnitude and direction.
Examples: velocity, acceleration, force,
torque, etc.
Vectors vs. Scalars
A scalar is just a number.
Examples: mass, volume, time, temperature, etc.
A vector is represented as a ray,or an arrow.
V
The initial end or tail
The terminal end or head
Picture of a Vector Named A
Magnitude of A
A = 10
Direction of A
q = 30 degrees
The Polar Angle for a Vector
Start at the positive x-axisand rotate counter-clockwise until you reach the vector.
That’s how you find the polar angle.
Two vectors A and B are equal if they have the same magnitude and direction.
A B
This property allows us to move vectors around on our paper/blackboard without changing their properties.
A = -B says that vectors A and B are anti-parallel. They have same size but the opposite direction.
A
B
A = -B also impliesB = -A
Graphical Addition of Vectors( Head –to Tail Addition )
To find C = A + B :1st Put the tail of B on the head of A.
2nd Draw the sum vector with its tail on the tail of A, and its head on the head of B.
Example: If C = A+B, draw C.
Here’s Vector C
Graphical Addition of Vectors( Head –to Tail Addition )
To find C = A - B :1st Put the tail of -B on the head of A.
2nd Draw the sum vector with its tail on the tail of A, and its head on the head of -B.
Example: If C = A-B, draw C.
Here’s Vector C = A - B
Addition of Many Vectors
A
BC D
AB
C
D
R
R = A + B + C + D
Add A,B,C, and D
Multiplication of a Vector by a Number.
A
2A-3A
Vector Addition by Components
(Do the math)
A vector A in the x-y plane can be represented by its perpendicular components called Ax and Ay.
x
y
A
AX
AY
Components AX and AY
can be positive, negative,or zero. The quadrantthat vector A lies indictates the sign of thecomponents.Components are scalars.
When the magnitude of vector A is given and its direction
specified then its componentscan be computed easily
x
y
A
AX
AYAX = Acosq
AY = Asinq
You must use the polar angle in these formulas.
Example: Find the x and y components of the vector shown ifA = 10 and q = 225 degrees.
AX = Acos = q 10 cos(225) = -7.07
Ay = Asin = q 10 sin(225) = -7.07
A = (-7.07, -7.07)
The magnitude and polar angle vector can be found by knowing its components
= tan-1(AY/AX) + C
A =
Example: Find A, and q if A = ( -7.07, -7.07)
== 10
= tan-1(AY/AX) + C = tan-1(-7.07/-7.07) + 180 = 225 degrees
Example: Find A, and q if A = ( 5.00, -4.00)
== 6.40
= tan-1(AY/AX) + C = tan-1(-4.00/5.00) + 360 = 321 degrees
Ax = Acosq
Ay = Asinq
If you know A and , q you can get Ax and Ay with:
If you know Ax and Ay
you can get A and q with:
A vector can be represented by its magnitude and angle, or its x and y components. You can go back and forth’from each representation with these formulas:
Adding Vectors by Components
If R = A + B
Then Rx = Ax + Bx
and Ry = Ay + By
So to add vectors, find their components and add the like components.
Example A = ( 3.00,2.00) and B = ( 0, 4.00)If R = A + B find the magnitude and direction of R.
Solution: R = A + B = ( 3.00,2.00) + ( 0, 4.00),
so R = ( 3.00, 6.00)
Then R = ( 32 + 62)1/2 = 6.70
q = tan-1( 6/3) = 63.4o
ExampleIf R = A + B find the magnitude and direction of R.
1st: Find the components of A and B.
Ax = 10cos 30 = 8.66 Ay = 10 sin30 = 5.00 Bx = 8cos 135 = -5.66 By = 8sin 135 = 5.66
2nd: Get Rx and Ry
Rx = Ax + Bx = 8.66 -5.66 = 3.00 Ry = Ay + By = 5.00 + 5.66 = 10.73rd: Get R and : q R = ( 32 + 10.72)1/2 = 11.1
q = tan-1 ( 10.7/3.00) = 74.3o
Ax = Acosq
Ay = Asinq
If you know A and , q you can get Ax and Ay with:
If you know Ax and Ay
you can get A and q with:
Summary
If R = A + B Rx = Ax + Bx
Ry = Ay + By
Unit Vectors
= ( 1, 0, 0) = ( 0, 1, 0 ) = ( 0, 0, 1)
Examples: A = (3,-2,5) = 3i - 2j + 5k
B = (3,0,5) = 3i + 5k
�̂�
The Scalar or Dot Product
Example: A = 3i +4j +5k B = 4i + 2j– 3k
A.B = 12 + 8 – 15 = 5
The Cross Product
A x B = i( Ay Bz - Az By ) - j( Ax Bz - Az Bx ) + k( Ax By - Ay Bx )
Example
A = (3,0,2) B = (1,1,0)
A X B = = i (0 -2) -j(0-2)+k(3-0)
= -2i +2j +3k = (-2,2,3)
Integrals of Vectors
dx + j
Example: If A = 3xi +5x2j , then find
+ j
Derivatives of Vectors
dA/dx = d (Ax, Ay, Az)/dx= (dAx/dx, dAy/dy, dAz/dz)
Example: If A = 3ti - 5t2j , then find dA/dt.
dA/dt = 3i -10tj
EXIT
If A = 6cos(3t)i +5cos(10t)j , then find