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Find a unit vector in the direction of the given vector. Verify that the result has a magnitude of 1. $$\mathbf{w}=\mathbf{i}-2 \mathbf{j}$$

Short Answer

Expert verified
The unit vector in the direction of the given vector \(\mathbf{w}=\mathbf{i}-2 \mathbf{j}\) is \(\frac{1}{\sqrt{5}}\mathbf{i} - \frac{2}{\sqrt{5}}\mathbf{j}\), and the magnitude of this unit vector is indeed 1.

Step by step solution

01

Calculate Magnitude or Length of the Vector

A vector's magnitude can be calculated using the Pythagorean theorem, which states that the sum of the squares of the lengths of two sides of a right triangle is equal to the square of the length of the hypotenuse. In terms of vectors, the magnitude of a vector \(\mathbf{w} = a\mathbf{i} + b\mathbf{j}\) is given by \(\sqrt{a^2 + b^2}\). Therefore, the magnitude of the vector \(\mathbf{w}=\mathbf{i}-2 \mathbf{j}\) is obtained by squaring the coefficients of \(\mathbf{i}\) and \(\mathbf{j},\) summing them up, and taking the square root of the sum. The magnitude (\(|\mathbf{w}|\)) will be \(\sqrt{1^2 + (-2)^2} = \sqrt{5}\).
02

Find the Unit Vector

After finding the magnitude, the next step is to find the unit vector. The unit vector in the direction of a given vector is obtained by dividing each component by the magnitude of the vector. Here, \(|\mathbf{w}|\) is \(\sqrt{5}\), so the unit vector \(u\) will be \(\mathbf{w}/ |\mathbf{w}| = (\mathbf{i}-2 \mathbf{j}) / \sqrt{5} = \frac{1}{\sqrt{5}}\mathbf{i} - \frac{2}{\sqrt{5}}\mathbf{j}\).
03

Verify the Magnitude of the Unit Vector

To finish the exercise, we need to verify that the magnitude of the unit vector calculated in the previous step is indeed 1. We compute the magnitude of the unit vector in the same way as before: squaring the coefficients of \(\mathbf{i}\) and \(\mathbf{j},\) summing them up, and taking the square root of the sum. The magnitude of the unit vector is \(\sqrt{(\frac{1}{\sqrt{5}})^2 +(-\frac{2}{\sqrt{5}})^2} = \sqrt{1/5 + 4/5} = 1\). Thus, the magnitude of the unit vector is indeed 1, which verifies our solution.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Vector Magnitude
Understanding the magnitude of a vector is crucial in vector operations. The magnitude, also known as the length of a vector, is computed using the Pythagorean theorem. It essentially quantifies how long the vector is in terms of its components. For any vector \( \mathbf{w} = a\mathbf{i} + b\mathbf{j} \), the magnitude is calculated as \( \sqrt{a^2 + b^2} \).

This formula mirrors the calculation of the hypotenuse in a right triangle. When you compare a vector's components to the sides of a right triangle, you're using these component values to identify the vector's total "length" or "size." In essence, the vector's magnitude gives you the distance of the vector from the origin (0,0) to its terminal point.
Pythagorean Theorem
The Pythagorean theorem is a foundational principle used to determine distances in various mathematical contexts, including vector calculations. This theorem simplifies finding the length of any vector by considering it as part of a right triangle.

In vector mathematics, the orthogonal components \( a \) and \( b \) of a vector are treated like the perpendicular sides of a triangle. The vector itself then acts as the hypotenuse. The Pythagorean theorem relates these by asserting that \( a^2 + b^2 = c^2 \), where \( c \) is the hypotenuse. When applied to a vector, this translates to finding the square root of the sum of the squares of its components to determine its magnitude.
Vector Components
Vector components are the building blocks that define the vector's direction and magnitude. In a two-dimensional space, a vector \( \mathbf{w} = a\mathbf{i} + b\mathbf{j} \) is defined by its horizontal component \( a\mathbf{i} \) and vertical component \( b\mathbf{j} \).

These components give us detailed information about the vector's direction. When you break down a vector, each component acts like a step that moves you along the x-axis and y-axis, respectively. The vector's overall impact is found by combining these steps, forming a pathway that extends from one point to another. Understanding these components allows you to manipulate vectors more effectively in calculations and applications.
Right Triangle
A right triangle forms the perfect analogy for working with vectors, especially in two-dimensional space. When a vector is drawn in a coordinate plane, its components naturally form the legs of a right triangle.

The horizontal component lies along the x-axis, while the vertical component aligns along the y-axis. The full vector, acting as the hypotenuse, extends diagonally from the origin to the endpoint dictated by these components. This geometric representation helps visualize how each part of a vector contributes to its overall direction and size. Understanding this relationship makes it easier to apply various mathematical principles, such as the Pythagorean theorem, in vector operations.

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Most popular questions from this chapter

Three forces with magnitudes of 70 pounds, 40 pounds, and 60 pounds act on an object at angles of \(-30^{\circ}, 45^{\circ},\) and \(135^{\circ},\) respectively, with the positive \(x\) -axis. Find the direction and magnitude of the resultant of these forces.

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A tractor pulls a log 800 meters, and the tension in the cable connecting the tractor and log is approximately 15,691 newtons. The direction of the force is \(35^{\circ}\) above the horizontal. Approximate the work done in pulling the log.

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