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This lecture explores the fundamental concepts of scalars and vectors, essential in physics. Scalars are quantities with only magnitudes, such as mass and temperature, while vectors have both magnitudes and directions, exemplified by displacement and velocity. We will cover graphical and analytical methods for adding and subtracting vectors, defining vector components, and utilizing unit vectors in a 3-dimensional Cartesian coordinate system. Additionally, we’ll discuss vector products, including the dot and cross product, and their implications in physics.
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PHY 430 – Lecture 2 Scalars & Vectors
3.1 Scalars & vectors • Scalars – quantities with only magnitudes • Eg. Mass, time, temperature • Mathematics - ordinary algebra • Vectors – quantities with magnitudes & directions • Eg. Displacement, velocity, acceleration • Mathematics - vector algebra
Two ways to specify a vector • 1. Give its componens, Vx and Vy • 2. Give its magnitud V and angle it makes with positive x – axis • We can shift from one description to the other by using theorem of Pythagoras and definition of tangent
Unit vectors • For 3-D Cartesian coordinate system • i = unit vector in the direction of x • j = unit vector in the direction of y • k = unit vector in the direction of z • Fig. 3-15
Products of vectors • Dot product: A B =IAIIBIcos A B = B A • Cross Product: A X B =IAIIBIsin n A x B = - B x A