Chapter 10: Problem 37
Find a unit vector orthogonal to both \(\vec{u}\) and \(\vec{v} .\) \(\vec{u}=\langle 5,0,2\rangle, \quad \vec{v}=\langle-3,0,7\rangle\)
Short Answer
Expert verified
The unit vector orthogonal to both \(\vec{u}\) and \(\vec{v}\) is \(\langle 0, -1, 0 \rangle\).
Step by step solution
01
Calculate the Cross Product
To find a vector orthogonal to both \( \vec{u} \) and \( \vec{v} \), find the cross product \( \vec{u} \times \vec{v} \). Use the formula: \(\vec{u} \times \vec{v} = \langle u_2v_3 - u_3v_2, u_3v_1 - u_1v_3, u_1v_2 - u_2v_1 \rangle\)Substitute the given vectors:\[ \vec{u} \times \vec{v} = \langle 0\cdot7 - 2\cdot0, 2\cdot(-3) - 5\cdot7, 5\cdot0 - 0\cdot(-3) \rangle = \langle 0, -41, 0 \rangle \]
02
Find the Magnitude of the Cross Product
Calculate the magnitude of the cross product vector \( \vec{u} \times \vec{v} = \langle 0, -41, 0 \rangle \) using the formula:\[ ||\vec{u} \times \vec{v}|| = \sqrt{0^2 + (-41)^2 + 0^2} = \sqrt{1681} = 41 \]
03
Normalize the Cross Product
To find the unit vector, divide the cross product by its magnitude. Normalize the vector \( \vec{u} \times \vec{v} = \langle 0, -41, 0 \rangle \):\[ \text{Unit vector} = \frac{1}{41} \langle 0, -41, 0 \rangle = \langle 0, -1, 0 \rangle \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vectors
In mathematics, vectors are fundamental elements used to describe quantities that have both a magnitude and direction. Many real-world concepts like force, velocity, and acceleration are represented as vectors. A vector is often denoted using arrow notation or brackets, such as \( \vec{u} = \langle a, b, c \rangle \) in three dimensions, representing a vector with components along the x, y, and z axes.
- The magnitude of a vector indicates the size or "length" of the vector, calculated using the Pythagorean theorem.
- The direction of a vector is shown by the orientation of the arrow or the sign of its components.
Orthogonality
Orthogonality is a key concept often used when discussing vectors, especially in the realm of linear algebra and geometry. Two vectors are orthogonal if they meet at a right angle, meaning their dot product is zero.
Consider vectors \( \vec{a} \) and \( \vec{b} \). These vectors are orthogonal if \( \vec{a} \cdot \vec{b} = 0 \). However, finding a vector specifically orthogonal to two other vectors involves calculating a cross product.
Consider vectors \( \vec{a} \) and \( \vec{b} \). These vectors are orthogonal if \( \vec{a} \cdot \vec{b} = 0 \). However, finding a vector specifically orthogonal to two other vectors involves calculating a cross product.
- Cross product results in a vector that is perpendicular to the plane formed by the initial two vectors.
- This is particularly useful in physics where determining a perpendicular vector aids in describing torque or rotational motion.
Unit Vector
A unit vector is a vector with a magnitude of exactly one unit and serves to indicate direction without affecting magnitude.
To convert any given vector into a unit vector, you "normalize" it, which means dividing the original vector by its own magnitude. For instance, given a vector \( \vec{v} = \langle x, y, z \rangle \), the unit vector \( \vec{u} \) is calculated as:
\[ \vec{u} = \frac{\vec{v}}{||\vec{v}||} \]
To convert any given vector into a unit vector, you "normalize" it, which means dividing the original vector by its own magnitude. For instance, given a vector \( \vec{v} = \langle x, y, z \rangle \), the unit vector \( \vec{u} \) is calculated as:
\[ \vec{u} = \frac{\vec{v}}{||\vec{v}||} \]
- Unit vectors are crucial in vector algebra as they allow the representation of directional information purely.
- They provide a standardized way to indicate direction, which is foundational in defining axes in coordinate systems like i, j, and k.
Magnitude of a Vector
The magnitude of a vector determines its length and is calculated by taking the square root of the sum of the squares of its components. It is always a non-negative value. If you have a vector \( \vec{v} = \langle a, b, c \rangle \), the magnitude is found using:
\[ ||\vec{v}|| = \sqrt{a^2 + b^2 + c^2} \]
\[ ||\vec{v}|| = \sqrt{a^2 + b^2 + c^2} \]
- The magnitude function maps a vector to a scalar value reflecting how much of the vector is present, akin to vector length.
- Understanding the magnitude is vital for scaling vectors and transforming them into unit vectors.