The Magnitude and Direction Angle of a Vector

Oct 13, 2025 by wbrum.org 106 views

Introduction

In this article, we will explore the concept of vector addition and how to find the magnitude and direction angle of the sum of two vectors. We will use the given information about the magnitude and direction angle of two vectors, ${$ \mathbf{r} $}$ and ${$ \mathbf{s} $}$, to find the magnitude and direction angle of their sum.

Vector Addition

Vector addition is a fundamental concept in mathematics and physics. It involves combining two or more vectors to form a new vector. The resulting vector is called the sum of the original vectors. In this case, we are given two vectors, ${$ \mathbf{r} $}$ and ${$ \mathbf{s} $}$, and we want to find their sum.

The Magnitude and Direction Angle of a Vector

Before we can find the sum of two vectors, we need to understand the concept of magnitude and direction angle. The magnitude of a vector is its length or size, while the direction angle is the angle between the vector and the positive x-axis.

The Magnitude of a Vector

The magnitude of a vector can be found using the following formula:

\|\mathbf{v}\| = \sqrt{x^2 + y^2}

where ${$ \mathbf{v}$] is the vector, [ $x\$] is the x-component of the vector, and \[$ y$] is the y-component of the vector.

The Direction Angle of a Vector

The direction angle of a vector can be found using the following formula:

\theta = \tan^{-1}\left(\frac{y}{x}\right)

where [ $\theta\$] is the direction angle, \[$ y$] is the y-component of the vector, and [$x$] is the x-component of the vector.

Finding the Magnitude and Direction Angle of the Sum

Now that we have a good understanding of the concept of magnitude and direction angle, we can find the magnitude and direction angle of the sum of two vectors.

Step 1: Convert the Direction Angles to Radians

The direction angles of the vectors [$ \mathbf{r} $}$ and ${$ \mathbf{s} $}$ are given in degrees. We need to convert them to radians before we can use them in our calculations.

\theta_r = \frac{270^\circ}{180^\circ} \pi = \frac{3\pi}{2}

\theta_s = \frac{71^\circ}{180^\circ} \pi = \frac{71\pi}{180}

Step 2: Find the x- and y-Components of the Vectors

We can find the x- and y-components of the vectors using the following formulas:

x_r = \|\mathbf{r}\| \cos(\theta_r)

y_r = \|\mathbf{r}\| \sin(\theta_r)

x_s = \|\mathbf{s}\| \cos(\theta_s)

y_s = \|\mathbf{s}\| \sin(\theta_s)

Step 3: Find the x- and y-Components of the Sum

We can find the x- and y-components of the sum using the following formulas:

x_{\text{sum}} = x_r + x_s

y_{\text{sum}} = y_r + y_s

Step 4: Find the Magnitude of the Sum

We can find the magnitude of the sum using the following formula:

\|\text{sum}\| = \sqrt{x_{\text{sum}}^2 + y_{\text{sum}}^2}

Step 5: Find the Direction Angle of the Sum

We can find the direction angle of the sum using the following formula:

\theta_{\text{sum}} = \tan^{-1}\left(\frac{y_{\text{sum}}}{x_{\text{sum}}}\right)

Calculating the Magnitude and Direction Angle of the Sum

Now that we have the formulas, we can plug in the values and calculate the magnitude and direction angle of the sum.

\|\mathbf{r}\| = 5

\|\mathbf{s}\| = 7

\theta_r = \frac{3\pi}{2}

\theta_s = \frac{71\pi}{180}

x_r = 5 \cos\left(\frac{3\pi}{2}\right) = 0

y_r = 5 \sin\left(\frac{3\pi}{2}\right) = -5

x_s = 7 \cos\left(\frac{71\pi}{180}\right) = 5.93

y_s = 7 \sin\left(\frac{71\pi}{180}\right) = 6.23

x_{\text{sum}} = x_r + x_s = 0 + 5.93 = 5.93

y_{\text{sum}} = y_r + y_s = -5 + 6.23 = 1.23

\|\text{sum}\| = \sqrt{x_{\text{sum}}^2 + y_{\text{sum}}^2} = \sqrt{(5.93)^2 + (1.23)^2} = 6.01

\theta_{\text{sum}} = \tan^{-1}\left(\frac{y_{\text{sum}}}{x_{\text{sum}}}\right) = \tan^{-1}\left(\frac{1.23}{5.93}\right) = 12.3^\circ

Conclusion

In this article, we have explored the concept of vector addition and how to find the magnitude and direction angle of the sum of two vectors. We have used the given information about the magnitude and direction angle of two vectors, ${$ \mathbf{r} $}$ and ${$ \mathbf{s} $}$, to find the magnitude and direction angle of their sum. We have also calculated the magnitude and direction angle of the sum using the formulas and values provided.

References

[1] "Vector Addition" by Khan Academy
[2] "Vector Addition" by Math Is Fun
[3] "Vector Addition" by Wolfram MathWorld

Note

Introduction

In our previous article, we explored the concept of vector addition and how to find the magnitude and direction angle of the sum of two vectors. In this article, we will answer some frequently asked questions about vector addition.

Q: What is vector addition?

A: Vector addition is a mathematical operation that combines two or more vectors to form a new vector. The resulting vector is called the sum of the original vectors.

Q: How do I add two vectors?

A: To add two vectors, you need to add their corresponding components. For example, if you have two vectors ${$ \mathbf{a} $}$ and ${$ \mathbf{b} $}$, you can add them by adding their x-components and y-components separately.

Q: What is the magnitude of a vector?

A: The magnitude of a vector is its length or size. It can be found using the formula:

\|\mathbf{v}\| = \sqrt{x^2 + y^2}

where [ $\mathbf{v}\$] is the vector, \[$ x$] is the x-component of the vector, and [$y$] is the y-component of the vector.

Q: What is the direction angle of a vector?

A: The direction angle of a vector is the angle between the vector and the positive x-axis. It can be found using the formula:

\theta = \tan^{-1}\left(\frac{y}{x}\right)

where [ $\theta\$] is the direction angle, \[$ y$] is the y-component of the vector, and [$x$] is the x-component of the vector.

Q: How do I find the magnitude and direction angle of the sum of two vectors?

A: To find the magnitude and direction angle of the sum of two vectors, you need to follow these steps:

Add the x-components of the two vectors.
Add the y-components of the two vectors.
Find the magnitude of the resulting vector using the formula:

\|\text{sum}\| = \sqrt{x_{\text{sum}}^2 + y_{\text{sum}}^2}

Find the direction angle of the resulting vector using the formula:

\theta_{\text{sum}} = \tan^{-1}\left(\frac{y_{\text{sum}}}{x_{\text{sum}}}\right)

Q: What are some common applications of vector addition?

A: Vector addition has many applications in physics, engineering, and computer science. Some common applications include:

Finding the position and velocity of an object in a two-dimensional or three-dimensional space.
Calculating the force and torque of a system of objects.
Modeling the motion of a particle or a system of particles.
Performing image processing and computer vision tasks.

Q: What are some common mistakes to avoid when working with vector addition?

A: Some common mistakes to avoid when working with vector addition include:

Failing to add the corresponding components of the vectors.
Failing to find the magnitude and direction angle of the resulting vector.
Using the wrong formula or method for finding the magnitude and direction angle.
Failing to check the units and dimensions of the vectors and the resulting vector.

Conclusion

In this article, we have answered some frequently asked questions about vector addition. We have also provided some common applications and mistakes to avoid when working with vector addition. By following the steps and formulas outlined in this article, you should be able to add vectors and find their magnitude and direction angle with confidence.

References

[1] "Vector Addition" by Khan Academy
[2] "Vector Addition" by Math Is Fun
[3] "Vector Addition" by Wolfram MathWorld

Note

The calculations and formulas used in this article are based on the assumption that the vectors are two-dimensional. If the vectors are three-dimensional, the calculations and formulas would be more complex.