Calculating the Magnitude of the Sum

Oct 13, 2025 by wbrum.org 29 views

Introduction

In this article, we will explore the concept of the magnitude of the sum of two perpendicular vectors. We will use the given information about the magnitudes of vectors $\vec{m}$ and $\vec{n}$ to calculate the magnitude of their sum. This problem is a classic example of how vectors can be used to represent physical quantities and how their properties can be used to solve real-world problems.

The Magnitude of Vectors

The magnitude of a vector is a measure of its size or length. It is denoted by the symbol $|\vec{v}|$ and is calculated using the formula:

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

where $x$ , $y$ , and $z$ are the components of the vector.

Given Information

We are given that the magnitude of vector $\vec{m}$ is 29.2 meters and the magnitude of vector $\vec{n}$ is 35.2 meters. We are also given that vectors $\vec{m}$ and $\vec{n}$ are perpendicular.

Calculating the Magnitude of the Sum

Since vectors $\vec{m}$ and $\vec{n}$ are perpendicular, their dot product is zero. The dot product of two vectors $\vec{a}$ and $\vec{b}$ is given by:

\vec{a} \cdot \vec{b} = |\vec{a}| |\vec{b}| \cos \theta

where $\theta$ is the angle between the two vectors.

Since the dot product of $\vec{m}$ and $\vec{n}$ is zero, we can write:

\vec{m} \cdot \vec{n} = |\vec{m}| |\vec{n}| \cos \theta = 0

This implies that $\cos \theta = 0$ , which means that $\theta = 90^\circ$ . This is consistent with the fact that vectors $\vec{m}$ and $\vec{n}$ are perpendicular.

Using the Pythagorean Theorem

To calculate the magnitude of the sum of vectors $\vec{m}$ and $\vec{n}$ , we can use the Pythagorean theorem. The Pythagorean theorem states that for a right-angled triangle with legs of length $a$ and $b$ and hypotenuse of length $c$ , the following equation holds:

a^2 + b^2 = c^2

In this case, the legs of the right-angled triangle are vectors $\vec{m}$ and $\vec{n}$ , and the hypotenuse is the sum of the two vectors.

Applying the Pythagorean Theorem

We can apply the Pythagorean theorem to calculate the magnitude of the sum of vectors $\vec{m}$ and $\vec{n}$ as follows:

|\vec{m} + \vec{n}|^2 = |\vec{m}|^2 + |\vec{n}|^2

Substituting the given values, we get:

|\vec{m} + \vec{n}|^2 = 29.2^2 + 35.2^2

Simplifying, we get:

|\vec{m} + \vec{n}|^2 = 851.84 + 1238.24

|\vec{m} + \vec{n}|^2 = 2090.08

Taking the square root of both sides, we get:

|\vec{m} + \vec{n}| = \sqrt{2090.08}

Simplifying, we get:

|\vec{m} + \vec{n}| = 45.76

Therefore, the magnitude of the sum of vectors $\vec{m}$ and $\vec{n}$ is 45.76 meters.

Conclusion

In this article, we used the given information about the magnitudes of vectors $\vec{m}$ and $\vec{n}$ to calculate the magnitude of their sum. We used the Pythagorean theorem to calculate the magnitude of the sum, and we found that it is 45.76 meters. This problem is a classic example of how vectors can be used to represent physical quantities and how their properties can be used to solve real-world problems.

References

[1] "Vector Calculus" by Michael Corral
[2] "Calculus" by Michael Spivak

Note

Q: What is the magnitude of the sum of two perpendicular vectors?

A: The magnitude of the sum of two perpendicular vectors can be calculated using the Pythagorean theorem. If the magnitudes of the two vectors are $a$ and $b$ , and they are perpendicular, then the magnitude of their sum is given by $\sqrt{a^2 + b^2}$ .

Q: How do I calculate the magnitude of the sum of two perpendicular vectors?

A: To calculate the magnitude of the sum of two perpendicular vectors, you need to follow these steps:

Calculate the magnitudes of the two vectors.
Add the squares of the magnitudes of the two vectors.
Take the square root of the result.

Q: What is the formula for the magnitude of the sum of two perpendicular vectors?

A: The formula for the magnitude of the sum of two perpendicular vectors is:

|\vec{m} + \vec{n}| = \sqrt{|\vec{m}|^2 + |\vec{n}|^2}

Q: Can I use the Pythagorean theorem to calculate the magnitude of the sum of two non-perpendicular vectors?

A: No, the Pythagorean theorem only applies to right-angled triangles, which means that the two vectors must be perpendicular. If the vectors are not perpendicular, you will need to use a different method to calculate the magnitude of their sum.

Q: What is the difference between the magnitude of the sum of two perpendicular vectors and the magnitude of the sum of two non-perpendicular vectors?

A: The magnitude of the sum of two perpendicular vectors is given by the Pythagorean theorem, while the magnitude of the sum of two non-perpendicular vectors is given by the law of cosines.

Q: Can I use the law of cosines to calculate the magnitude of the sum of two perpendicular vectors?

A: No, the law of cosines is used to calculate the magnitude of the sum of two non-perpendicular vectors, not perpendicular vectors. The Pythagorean theorem is used to calculate the magnitude of the sum of two perpendicular vectors.

Q: What is the law of cosines?

A: The law of cosines is a formula that is used to calculate the magnitude of the sum of two non-perpendicular vectors. It is given by:

|\vec{a} + \vec{b}|^2 = |\vec{a}|^2 + |\vec{b}|^2 + 2 |\vec{a}| |\vec{b}| \cos \theta

where $\theta$ is the angle between the two vectors.

Q: Can I use the law of cosines to calculate the magnitude of the sum of two perpendicular vectors?

Q: What is the difference between the Pythagorean theorem and the law of cosines?

A: The Pythagorean theorem is used to calculate the magnitude of the sum of two perpendicular vectors, while the law of cosines is used to calculate the magnitude of the sum of two non-perpendicular vectors.

Q: Can I use the Pythagorean theorem to calculate the magnitude of the sum of two vectors in 3D space?

A: No, the Pythagorean theorem only applies to right-angled triangles in 2D space. To calculate the magnitude of the sum of two vectors in 3D space, you will need to use a different method, such as the distance formula.

Q: What is the distance formula?

A: The distance formula is a formula that is used to calculate the distance between two points in 3D space. It is given by:

d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2 + (z_2 - z_1)^2}

where $(x_1, y_1, z_1)$ and $(x_2, y_2, z_2)$ are the coordinates of the two points.

Q: Can I use the distance formula to calculate the magnitude of the sum of two vectors in 3D space?

A: Yes, the distance formula can be used to calculate the magnitude of the sum of two vectors in 3D space. However, it is not as straightforward as using the Pythagorean theorem for 2D vectors.