Chapter 1: Problem 3
The vectors \(\mathbf{A}, \mathbf{B}, \mathbf{C}\) are coplanar. Show graphically that $$ \mathbf{A} \cdot(\mathbf{B}+\mathbf{C})=\mathbf{A} \cdot \mathbf{B}+\mathbf{A} \cdot \mathbf{C} $$
Short Answer
Expert verified
Graphically, the projection of \(\mathbf{B} + \mathbf{C}\) onto \(\mathbf{A}\) has the same length as the sum of the projections of \(\mathbf{B}\) and \(\mathbf{C}\) onto \(\mathbf{A}\), confirming the distributive property of the dot product.
Step by step solution
01
Understand Vector Dot Product
The dot product of two vectors is a scalar quantity that is the product of the magnitude of the first vector and the magnitude of the projection of the second vector onto the first. The dot product is distributive over vector addition, which means \(\mathbf{X} \cdot (\mathbf{Y} + \mathbf{Z}) = \mathbf{X} \cdot \mathbf{Y} + \mathbf{X} \cdot \mathbf{Z}\).
02
Illustrate Vectors on a Plane
Draw vectors \(\mathbf{A}\), \(\mathbf{B}\), and \(\mathbf{C}\) originating from the same point on a plane since they are coplanar. Ensure that the vectors are accurately represented with directed line segments.
03
Show Vector Addition Graphically
Using the tip-to-tail method, draw \(\mathbf{B} + \mathbf{C}\) by placing the tail of \(\mathbf{C}\) at the tip of \(\mathbf{B}\). The resultant vector drawn from the tail of \(\mathbf{B}\) to the tip of \(\mathbf{C}\) represents \(\mathbf{B} + \mathbf{C}\).
04
Depict the Dot Product Graphically
Next, draw the projection of \(\mathbf{B} + \mathbf{C}\) onto \(\mathbf{A}\), as well as the projections of \(\mathbf{B}\) and \(\mathbf{C}\) onto \(\mathbf{A}\) separately. The lengths of these projections represent the respective dot product magnitudes.
05
Verify Distributive Property Graphically
Observe that the length of the projection of \(\mathbf{B} + \mathbf{C}\) onto \(\mathbf{A}\) is equal to the sum of the lengths of the projections of \(\mathbf{B}\) and \(\mathbf{C}\) onto \(\mathbf{A}\). This visual representation confirms the equation \(\mathbf{A} \cdot (\mathbf{B} + \mathbf{C}) = \mathbf{A} \cdot \mathbf{B} + \mathbf{A} \cdot \mathbf{C}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distributive Property of Vectors
The distributive property is a mathematical principle that applies to many operations, including the vector dot product. When it comes to vectors, this property allows us to distribute the dot product over a sum of vectors. In simpler terms, if you have a vector \textbf{A} and are taking the dot product with the sum of two other vectors, \textbf{B} and \textbf{C}, you can compute the dot product of each pair individually and then sum the results. It's essentially a way to break down a more complex operation into simpler steps.
Mathematically, this is expressed as \( \mathbf{A} \cdot (\mathbf{B} + \mathbf{C}) = \mathbf{A} \cdot \mathbf{B} + \mathbf{A} \cdot \mathbf{C} \). The property holds for any number of vectors added together, and it is extremely useful for simplifying calculations in physics and engineering, where vectors are often combined.
Mathematically, this is expressed as \( \mathbf{A} \cdot (\mathbf{B} + \mathbf{C}) = \mathbf{A} \cdot \mathbf{B} + \mathbf{A} \cdot \mathbf{C} \). The property holds for any number of vectors added together, and it is extremely useful for simplifying calculations in physics and engineering, where vectors are often combined.
Vector Addition
Adding two vectors together is a fundamental operation in vector algebra. To add vectors, you simply align them head to tail and draw a new vector from the free tail to the free head. This new vector is called the resultant vector, and it effectively combines the magnitude and direction of the original vectors. This method is known as the tip-to-tail method.
The graphical method of vector addition not only helps in visualizing the vectors and their resultant but also in applying other vector operations like the dot product. It's very important to understand that vector addition is defined geometrically, and it is different from adding scalars because it takes into account both magnitude and direction.
The graphical method of vector addition not only helps in visualizing the vectors and their resultant but also in applying other vector operations like the dot product. It's very important to understand that vector addition is defined geometrically, and it is different from adding scalars because it takes into account both magnitude and direction.
Scalar Quantity
Unlike vectors, which have both magnitude and direction, scalar quantities possess only magnitude. Examples of scalar quantities include temperature, mass, and time. In the context of vector multiplication, the dot product of two vectors yields a scalar quantity, not a vector. This scalar represents the product of the magnitudes of the two vectors and the cosine of the angle between them.
The scalar outcome of a dot product can be very telling; it can indicate whether two vectors are orthogonal (if the product is zero), how much one vector extends in the direction of another, or the projection of one vector onto another. Understanding the difference between vectors and scalars is crucial for grasping the various ways in which they interact in mathematical operations.
The scalar outcome of a dot product can be very telling; it can indicate whether two vectors are orthogonal (if the product is zero), how much one vector extends in the direction of another, or the projection of one vector onto another. Understanding the difference between vectors and scalars is crucial for grasping the various ways in which they interact in mathematical operations.
Graphical Representation of Vectors
Illustrating vectors graphically allows for an intuitive understanding of vector operations. In a graphical representation, vectors are usually depicted as directed line segments. The direction of the arrow shows the direction of the vector, while its length represents the vector's magnitude, often drawn to a specific scale.
The visual approach is beneficial when learning about vector addition and the distributive property because it provides a clear picture of how vectors combine and interact. This can be especially helpful when dealing with the vector dot product, as projections can be visually analyzed and compared. A well-drawn vector diagram can serve as a powerful tool for both explanation and confirmation of vector operations.
The visual approach is beneficial when learning about vector addition and the distributive property because it provides a clear picture of how vectors combine and interact. This can be especially helpful when dealing with the vector dot product, as projections can be visually analyzed and compared. A well-drawn vector diagram can serve as a powerful tool for both explanation and confirmation of vector operations.