Chapter 14: Problem 4
State the position vectors of the points with coordinates \((9,1,-1)\) and \((-4,0,4)\),
Short Answer
Expert verified
The position vectors are \(\vec{r_1} = 9i + 1j - 1k\) and \(\vec{r_2} = -4i + 0j + 4k\).
Step by step solution
01
Understanding Position Vectors
Position vectors are used to represent points in a coordinate system relative to the origin. Given a 3-dimensional point \(x, y, z\), its position vector is written in the form of \(\vec{r} = xi + yj + zk\), where \(i, j, k\) are the unit vectors along the x, y, and z axes respectively.
02
Finding Position Vector for Point (9, 1, -1)
For the point with coordinates \(9, 1, -1\), the position vector is formed using its components as coefficients of the unit vectors. Thus, the position vector is \(\vec{r_1} = 9i + 1j - 1k\).
03
Finding Position Vector for Point (-4, 0, 4)
For the point with coordinates \(-4, 0, 4\), similarly, the position vector is formed. It will be \(\vec{r_2} = -4i + 0j + 4k\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
3-dimensional coordinates
When discussing points in space, we often refer to their 3-dimensional coordinates. These coordinates are expressed as \(x, y, z\) and help us locate points precisely in a 3-dimensional space, much like giving a street address helps locate a house in a city. Each coordinate corresponds to the position along the respective x, y, or z axis in a Cartesian coordinate system.
- The x-coordinate tells us how far along the x-axis (left-right) the point is.
- The y-coordinate indicates the location along the y-axis (up-down).
- The z-coordinate represents the depth or motion along the z-axis (in-out).
vector representation
Vectors are incredible tools in mathematics and physics, offering a way to depict both magnitude and direction. A vector in 3-dimensional space, like a position vector, is typically represented in terms of its components along the x, y, and z axes. For a vector pointing from the origin to the point \(x, y, z\), the vector is described as \(\vec{r} = xi + yj + zk\).
- Here, \(i, j, k\) are unit vectors that align with the x, y, and z axes respectively.
- The coefficients \(x, y, z\) provide the scale or size of the vector in each direction.
unit vectors
Unit vectors play a crucial role in the vector representation by defining direction without concerning magnitude. They have a magnitude of one and inform us precisely which direction a particular axis is pointing. In the context of 3-dimensional coordinates, we use the unit vectors: \(i, j, k\).
- The unit vector \(i\) points in the direction of the x-axis.
- The unit vector \(j\) points in the direction of the y-axis.
- The unit vector \(k\) points in the direction of the z-axis.
coordinate system
To discuss points and vectors in space, it's essential to understand the coordinate system, particularly the Cartesian system used in 3-dimensional space. It consists of three perpendicular axes: the x, y, and z axes, intersecting at a point known as the origin.
- The origin is the reference point, usually denoted as \((0, 0, 0)\).
- The x-axis runs horizontally; the y-axis runs vertically.
- The z-axis adds depth, making the system 3-dimensional.