8.3
向量
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Q1: What is the difference between a vector and a scalar?
Vectors possess both magnitude and direction, while scalars are defined solely by magnitude. For example, velocity of 50 km/hr east is a vector because it specifies both speed and direction. Scalars like temperature have only numerical value without directional information.
Q2: How are vectors represented in the coordinate plane?
Vectors are represented as ordered pairs of horizontal and vertical components enclosed in angle brackets. If a vector has initial point A at coordinates (x1, y1) and terminal point B at (x2, y2), the vector components are derived from these coordinates. This representation simplifies calculations involving vector operations.
Q3: What does it mean for two vectors to be equal?
Two vectors are equal when they have the same magnitude and the same direction, regardless of their initial positions. Magnitude indicates strength, while direction specifies orientation in space. Equal vectors may be located at different points in the plane but maintain identical properties.
Q4: How do you add two vectors geometrically?
Vector addition can be performed by positioning one vector's initial point at the other's terminal point to form the resultant. Alternatively, if both vectors originate from the same point, their sum is represented by the diagonal of the parallelogram they form, starting from that common point.
Q5: What happens when you multiply a vector by a negative scalar?
Multiplying a vector by a negative scalar reverses the vector's direction while affecting its magnitude. For instance, if vector v is multiplied by -2, the resultant vector points in the opposite direction and is twice as long. This operation is fundamental to vector subtraction.
Q6: How is vector magnitude calculated from components?
Vector magnitude is derived using the Pythagorean theorem. For a vector v with components ⟨a, b⟩, the magnitude equals the square root of a² plus b². This formula applies to any vector represented in the Cartesian plane with horizontal and vertical components.
Q7: What are unit vectors and how are they used?
Unit vectors are vectors with length one, typically denoted as i for the horizontal component and j for the vertical component. A vector v can be expressed as a linear combination of unit vectors, where a and b represent the horizontal and vertical components. This representation simplifies calculations involving the dot product and other vector operations.