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Vectors. Scalars & Vectors. Vectors Quantity with both magnitude & direction Does NOT follow elementary arithmetic/algebra rules Examples – position, force, moment, velocities, acceleration. Magnitude. Head. Direction/Angle. Tail. Line of Action. Parallelogram Law.
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Scalars & Vectors • Vectors • Quantity with both magnitude & direction • Does NOT follow elementary arithmetic/algebra rules • Examples – position, force, moment, velocities, acceleration Magnitude Head Direction/Angle Tail Line of Action
Parallelogram Law • The resultant of two forces can be obtained by • Joining the vectors at their tails A A+B • Constructing a parallelogram B • The resultant is the diagonal of the parallelogram
Triangle Construction • The resultant of two forces can be obtained by • Joining the vectors in tip-to-tail fashion A B R • The resultant extends from the tail of A to the head of the B
Vector Addition • Does A + B = B + A ? A B R R A B YES! - commutative
Vector Subtraction A-B = A + (-B) A -B B -B R A
Vector Subtraction • Does A – B = B - A ? -B B R -R A -A NO! – opposite sense
Vector Operations • Multiplication & Division of Vector (A) by Scalar (a) a * A = aA 2A 2 * A = 2A A -.5 * A = -.5A A -.5A
Representation of a Vector Given the points and , the vector a with representation is a Find the vector represented by the directed line segment with initial point A(2,-3,4) and terminal point B(-2,1,1).
Magnitude of a vector Determine the magnitude of the following:
Parallel • Two vectors are parallel to each other if one is the scalar multiple of the other. Determine if the two vectors are parallel These are parallel since b= -3a These are not parallel since 4(1/2) =2 , but 10(1/2)=5 not -9
Unit vectors Any vector that has a magnitude of 1 is considered a unit vector. Can you think of a unit vector?
Standard Basis Vectors Example- Write in terms of the standard basis vector i,j,k.
Example If a = i + 2j - 3k and b = 4i + 7k, express the vector 2a+3b in terms of i,j,k. 2a+3b=2(i + 2j - 3k)+3(4i + 7k) 2a+3b=2i + 4j - 6k+ 12i + 21k 2a+3b=14i+4j+15k
Unit Vectors The unit vector in the same direction of a is Find a unit vector in the same direction as 2i – j – 2k. We are looking for a vector in the same direction as the original vector, but is also a unit vector. Let’s first find the magnitude Check? Same direction? Magnitude = 1?
Homework • P649 • 4,5,7,9,11,15,17,19