Chapter 5: Problem 29
If \(\mathbf{u}=3 \mathbf{i}-\mathbf{j}\) and \(\mathbf{v}=2 \mathbf{i}+4 \mathbf{j},\) find the horizontal and the vertical components of the indicated vector. $$ 2 \mathbf{u}-\mathbf{v} $$
Short Answer
Expert verified
The horizontal component is 4, and the vertical component is -6.
Step by step solution
01
Understanding Vectors
Vectors are expressions that represent quantities having both magnitude and direction. The vector \( \mathbf{u} = 3 \mathbf{i} - \mathbf{j} \) consists of a horizontal component \( 3 \mathbf{i} \) and a vertical component \( - \mathbf{j} \), while the vector \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) consists of horizontal component \( 2 \mathbf{i} \) and a vertical component \( 4 \mathbf{j} \).
02
Multiply Vector \(\mathbf{u}\) by 2
To find \(2 \mathbf{u}\), multiply each component of \(\mathbf{u}\) by 2. This gives us: \[ 2 \mathbf{u} = 2(3 \mathbf{i} - \mathbf{j}) = 6 \mathbf{i} - 2 \mathbf{j} \]
03
Subtract Vector \(\mathbf{v}\) from \(2 \mathbf{u}\)
Now, subtract the vector \(\mathbf{v}\) from the vector \(2 \mathbf{u}\): \[ 2 \mathbf{u} - \mathbf{v} = (6 \mathbf{i} - 2 \mathbf{j}) - (2 \mathbf{i} + 4 \mathbf{j}) \] When subtracting, subtract corresponding components: \[ = (6 - 2) \mathbf{i} + (-2 - 4) \mathbf{j} = 4 \mathbf{i} - 6 \mathbf{j} \]
04
Identify the Horizontal and Vertical Components
After performing the operations, the resulting vector is \(4 \mathbf{i} - 6 \mathbf{j}\). The horizontal component is the coefficient of \(\mathbf{i}\), which is \(4\). The vertical component is the coefficient of \(\mathbf{j}\), which is \(-6\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Horizontal Component
A vector's horizontal component indicates its direction along the x-axis. It is usually represented by a term involving the unit vector \( \mathbf{i} \). In the exercise above, the horizontal component helps us understand how far the vector moves from side to side.
For the vector \( \mathbf{u} = 3 \mathbf{i} - \mathbf{j} \), the horizontal component is \( 3 \mathbf{i} \). Similarly, the horizontal part of \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) is \( 2 \mathbf{i} \).
For the vector \( \mathbf{u} = 3 \mathbf{i} - \mathbf{j} \), the horizontal component is \( 3 \mathbf{i} \). Similarly, the horizontal part of \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) is \( 2 \mathbf{i} \).
- In vector arithmetic, when vectors are scaled (like multiplying \( \mathbf{u} \) by 2), each component must be scaled accordingly. This keeps the direction and balance intact.
- So, multiplying \( \mathbf{u} \) by 2 gives \( 6 \mathbf{i} \), representing the enhanced horizontal movement.
- In the final computation of \( 2 \mathbf{u} - \mathbf{v} \), subtracting \( 2 \mathbf{i} \) from \( 6 \mathbf{i} \) results in \( 4 \mathbf{i} \), defining the net horizontal motion of the vector.
Vertical Component
The vertical component of a vector shows its movement along the y-axis, represented by the unit vector \( \mathbf{j} \). Think of it like how far a vector will move up or down.
For the initial vector \( \mathbf{u} = 3 \mathbf{i} - \mathbf{j} \), the vertical component is \( -\mathbf{j} \), indicating a downward movement. In contrast, the vector \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) has a vertical component of \( 4 \mathbf{j} \), suggesting upward movement.
For the initial vector \( \mathbf{u} = 3 \mathbf{i} - \mathbf{j} \), the vertical component is \( -\mathbf{j} \), indicating a downward movement. In contrast, the vector \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) has a vertical component of \( 4 \mathbf{j} \), suggesting upward movement.
- When multiplying vector \( \mathbf{u} \) by 2, the vertical component becomes \( -2 \mathbf{j} \). This shifts the vector further down.
- Subtracting \( 4 \mathbf{j} \) from \( -2 \mathbf{j} \) during subtraction results in \( -6 \mathbf{j} \), showing an overall downward trend in the result.
Vector Subtraction
Vector subtraction is a process of determining the difference between two vectors. It is similar to vector addition but involves subtracting corresponding components of each vector.
When subtracting \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) from \( 2 \mathbf{u} \), you need to counterbalance each component individually: horizontal minus horizontal, and vertical minus vertical.
When subtracting \( \mathbf{v} = 2 \mathbf{i} + 4 \mathbf{j} \) from \( 2 \mathbf{u} \), you need to counterbalance each component individually: horizontal minus horizontal, and vertical minus vertical.
- The operation \( 6 \mathbf{i} - 2 \mathbf{i} = 4 \mathbf{i} \) gives the net horizontal component.
- Similarly, \( -2 \mathbf{j} - 4 \mathbf{j} = -6 \mathbf{j} \) result in the net vertical component.
- This ensures both magnitude and direction are taken into account, reflecting a true change from one vector to another.