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Chapter 3. Vectors and Coordinate Systems. Our universe has three dimensions, so some quantities also need a direction for a full description. For example, wind has both a speed and a direction; hence the motion of the wind is described by a vector.
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Chapter 3. Vectors and Coordinate Systems Our universe has three dimensions, so some quantities also need a direction for a full description. For example, wind has both a speed and a direction; hence the motion of the wind is described by a vector. Chapter Goal: To learn how vectors are represented and used.
Student Learning Objectives – Ch. 3 • To understand the basic properties of vectors. • To add and subtract vectors both graphically and using components. • To be able to decompose a vector into its components and to reassemble vector components into a magnitude and a direction. • To recognize and use the basic unit vectors. • To work with tilted coordinate systems.
Vector Addition Problem • Which figure shows A1 + A2 + A3?
Vector Subtraction • Which figure shows 2A – B?
Magnitude of A: A= (Ax2 + Ay2)1/2 Direction of A: θ = tan-1 (Ay/Ax)
What are the x- and y-components Cx and Cy of vector ? Cx = 1 cm, Cy = –1 cm Cx= –3 cm, Cy = 1 cm Cx = –2 cm, Cy = 1 cm Cx= –4 cm, Cy = 2 cm Cx= –3 cm, Cy = –1 cm
What are the x- and y-components Cx and Cy of vector ? Cx = 1 cm, Cy = –1 cm Cx= –3 cm, Cy = 1 cm Cx = –2 cm, Cy = 1 cm Cx= –4 cm, Cy = 2 cm Cx= –3 cm, Cy = –1 cm
Tilted axes • Often is it convenient to tilt the coordinate axes (to represent an object on an incline for example). • The axes stay perpendicular to each other. • The unit vectors corespond to axes, not to “horizontal and vertical” so they are also tilted.
Tilted axes • Cx = C cos θ • Cy = C sin θ • Note that θ is defined relative to the tilted x-axis and not to “horizontal”
Angle φthat specifies the direction of is given by tan–1(Cy /Cx) tan–1(Cx /|Cy|) tan–1(Cy /|Cx|) tan–1(Cx /Cy) tan–1(|Cx |/|Cy|)
Angle φthat specifies the direction of is given by tan–1(Cy /Cx) tan–1(Cx /|Cy|) tan–1(Cy /|Cx|) tan–1(Cx /Cy) tan–1(|Cx |/|Cy|)