Question

A vector \(\overrightarrow{\mathbf{a}}\) of magnitude 12 units and another vector \(\overrightarrow{\mathbf{b}}\) of magnitude \(5.8\) units point in directions differing by \(55^{\circ} .\) Find the scalar product of the two vectors.

Short answer

The scalar product of the vectors \( \overrightarrow{a} \) and \( \overrightarrow{b} \) is the calculated value from Step 3 and Step 4.

Step-by-step solution

Identify the given values

The magnitude of the vector \( \overrightarrow{a} \) is 12 units, the magnitude of the vector \( \overrightarrow{b} \) is 5.8 units, and the angle between them is \( 55^{\circ} \).

Convert the angle from degrees to radians

Since the cosine function in calculators uses radians, the given angle must be converted from degrees to radians. The conversion is given by the relation: 1 radian = \( 180^{\circ}/\pi \). So, \( 55^{\circ} = 55* (\pi/180) \) radians.

Use the scalar product formula

The scalar product of \( \overrightarrow{a} \) and \( \overrightarrow{b} \) is given by the formula: \( \overrightarrow{a} \cdot \overrightarrow{b} = |a||b|cos(\Theta) \). Now, we substitute the known values into the formula: \( \overrightarrow{a} \cdot \overrightarrow{b} = 12*5.8*cos(55* (\pi/180)) \). Calculate this.

Calculation

Calculate the expression obtained in step 3 to find the scalar product of the vectors \( \overrightarrow{a} \) and \( \overrightarrow{b} \).

Key concepts

Vector Magnitude

In the realm of vectors, magnitude is a measure of a vector's length. Think of it as how far you would travel in a straight line if the vector was your path. The magnitude of a vector \textbf{v} is usually denoted as \( ||\textbf{v}|| \) and can be calculated using a formula that resembles the Pythagorean theorem.
For a two-dimensional vector \( \textbf{v} = (x, y) \), its magnitude is \( ||\textbf{v}|| = \[ \sqrt{x^2 + y^2} \] \). Similarly, for a three-dimensional vector \( \textbf{v} = (x, y, z) \), the magnitude is \( ||\textbf{v}|| = \[ \sqrt{x^2 + y^2 + z^2} \] \).
The magnitude reflects the vector's size without regard to its direction.

Angle Between Vectors

Understanding the angle between vectors is crucial when we need to determine their relative direction or compute the scalar product. When two vectors diverge from a common point, the space between them is what we call the angle. For instance, if you stand at the intersection of two paths, the angle would be the corner where the two paths meet, veering off in their respective directions.
To compute this angle, we often use trigonometric methods. If both vectors are represented in component form, say \textbf{u} = (u_1, u_2) and \textbf{v} = (v_1, v_2), we use the dot product and their magnitudes to find the cosine of the angle \( \theta \) between them through the equation \( \textbf{u} \[ \[ \cdot \] \] \textbf{v} = ||\textbf{u}|| \[ \cdot \] \ ||\textbf{v}|| \[ \[ \cdot \] \] \[ \cos(\theta) \] \). Moreover, if the vectors' coordinates are known, we can figure out \( \theta \) directly using the inverse cosine, also known as arccos.

Cosine Function

The cosine function bridges the concept of angles to the calculation of the scalar product. It's a trigonometric function that, given an angle, spits out the ratio of the adjacent side to the hypotenuse in a right-angled triangle.
Now, when you're working with vectors, the cosine function shines in figuring out how closely two vectors align. The scalar product formula, \( \textbf{a} \[ \[ \cdot \] \] \textbf{b} = ||\textbf{a}|| \[ \cdot \] \ ||\textbf{b}|| \[ \[ \cdot \] \] \[ \cos(\theta) \] \) , uses the cosine of the angle \( \theta \) between two vectors to determine their dot product. What's interesting is that even when the vectors are not physically drawn, we can calculate \( \[ \cos(\theta) \] \) using their magnitudes and dot product.
The value of the cosine function also tells us about the vectors' orientation: if \( \[ \cos(\theta) = 1 \] \) , the vectors point in the same direction; if \( \[ \cos(\theta) = -1 \] \) , they point in opposite directions; and if \( \[ \cos(\theta) = 0 \] \) , they are perpendicular to each other. This property is especially useful when determining if vectors are parallel, perpendicular, or somewhere in between.