Chapter 7: Problem 41
Vector \(\mathbf{V}\) is in standard position, and makes an angle of \(40^{\circ}\) with the positive \(x\)-axis. Its magnitude is 18 . Write \(\mathbf{V}\) in component form \(\langle a, b\rangle\) and in vector component form \(a \mathbf{i}+b \mathbf{j}\).
Short Answer
Expert verified
\( \mathbf{V} = \langle 13.788, 11.574 \rangle \) or \( \mathbf{V} = 13.788 \mathbf{i} + 11.574 \mathbf{j} \).
Step by step solution
01
Understanding Vector Components
To express a vector in component form, we need to find the horizontal and vertical components of the vector. These are determined using its angle with the positive x-axis and its magnitude. The components can be expressed as \( \langle a, b \rangle \), where \( a \) is the horizontal component and \( b \) is the vertical component.
02
Calculating the Horizontal Component
The horizontal component \( a \) is calculated using cosine of the angle. The formula is: \( a = \| \mathbf{V} \| \cos(\theta) \). Here, \( \| \mathbf{V} \| = 18 \) and \( \theta = 40^{\circ} \). Calculate: \( a = 18 \cos(40^{\circ}) \).
03
Calculating the Vertical Component
The vertical component \( b \) is calculated using sine of the angle. The formula is: \( b = \| \mathbf{V} \| \sin(\theta) \). Using \( \| \mathbf{V} \| = 18 \) and \( \theta = 40^{\circ} \), calculate \( b = 18 \sin(40^{\circ}) \).
04
Calculating the Cosine and Sine Values
Use a calculator to find \( \cos(40^{\circ}) \) which is approximately 0.766, and \( \sin(40^{\circ}) \) which is approximately 0.643.
05
Finalize Components
Substitute the cosine and sine values into the component formulas: \( a = 18 \times 0.766 = 13.788 \) and \( b = 18 \times 0.643 = 11.574 \). Thus, the vector in component form is \( \langle 13.788, 11.574 \rangle \).
06
Writing in Vector Component Form
Using the components \( a \) and \( b \), express the vector in the form \( a \mathbf{i} + b \mathbf{j} \). Therefore, \( \mathbf{V} = 13.788 \mathbf{i} + 11.574 \mathbf{j} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Magnitude
Magnitude describes the overall size or length of a vector. It is a measurement of how far the vector extends in space, regardless of its direction. For a vector \(\mathbf{V}\), the magnitude is often denoted by \(|\mathbf{V}|\) and is typically found using the Pythagorean theorem or other formulas involving the vector’s components if they are known.
- When given as a scalar, the magnitude does not affect direction, but simply indicates the size.
- In this exercise, the vector \(\mathbf{V}\) has a magnitude of 18, which tells us that the vector is 18 units long.
Angle with x-axis
The angle a vector makes with the x-axis is crucial in determining its direction in a plane. This angle, measured in degrees or radians, tells how slanted the vector is relative to the positive x-axis.
- In this exercise, the vector \(\mathbf{V}\) makes a 40° angle with the positive x-axis.
- This angle helps in using trigonometric functions to find the vector's components.
Component Form
Component form of a vector breaks it down into its horizontal and vertical parts. Expressing a vector in component form makes it easy to perform calculations and visualize in two-dimensional space.
- It is denoted as \(\langle a, b \rangle\), where \(a\) and \(b\) are the components along the x and y axes, respectively.
- This form allows us to see how much the vector moves along each axis separately.
Horizontal Component
The horizontal component of a vector, represented as \(a\), shows how much the vector extends along the x-axis.
- Calculated using the cosine trigonometric function: \(a = |\mathbf{V}| \cos(\theta)\).
- In the example given, we use \(\cos(40^{\circ})\) to find that \(a = 18 \times 0.766\) which gives approximately 13.788.
Vertical Component
The vertical component, denoted as \(b\), indicates the amount of the vector's magnitude projected along the y-axis.
- It utilizes the sine function: \(b = |\mathbf{V}| \sin(\theta)\).
- For our problem, we calculate this by \(b = 18 \times 0.643\), yielding approximately 11.574.
Trigonometric Functions
Trigonometric functions, specifically sine and cosine, play a vital role in vector mathematics. They help resolve vectors into their respective components.
- Cosine corresponds to the horizontal direction: \(\cos(\theta) = \frac{\text{adjacent}}{\text{hypotenuse}}\).
- Sine correlates with the vertical component: \(\sin(\theta) = \frac{\text{opposite}}{\text{hypotenuse}}\).