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An object experiences two velocity vectors in its environment:

[tex]\[
\begin{array}{l}
v_1 = -60i + 3j \\
v_2 = 4i + 14j
\end{array}
\][/tex]

What is the true speed and direction of the object? Round the speed to the thousandths place and the direction to the nearest degree.

A. [tex]$58.524; 163^{\circ}$[/tex]
B. [tex]$58.524; 17^{\circ}$[/tex]
C. [tex]$53.357; 163^{\circ}$[/tex]
D. [tex]$53.357; 17^{\circ}$[/tex]


Sagot :

Certainly! Let's determine the true speed and direction of the object by combining the given velocity vectors. Here are the steps to solve this problem:

### Step 1: Sum the Components of the Velocity Vectors

Given vectors are:
[tex]\[ v_1 = -60i + 3j \][/tex]
[tex]\[ v_2 = 4i + 14j \][/tex]

First, sum the [tex]\(i\)[/tex]-components and [tex]\(j\)[/tex]-components of the two vectors:

[tex]\[ v_{\text{total}, i} = -60 + 4 = -56 \][/tex]
[tex]\[ v_{\text{total}, j} = 3 + 14 = 17 \][/tex]

Thus, the resultant vector is:
[tex]\[ v_{\text{total}} = -56i + 17j \][/tex]

### Step 2: Calculate the Magnitude (True Speed) of the Resultant Vector

The magnitude or true speed [tex]\(s\)[/tex] of the resultant vector is given by the Euclidean norm:

[tex]\[ s = \sqrt{v_{\text{total}, i}^2 + v_{\text{total}, j}^2} \][/tex]

Substituting the values:

[tex]\[ s = \sqrt{(-56)^2 + 17^2} \][/tex]
[tex]\[ s = \sqrt{3136 + 289} \][/tex]
[tex]\[ s = \sqrt{3425} \][/tex]

Calculating the square root and rounding to the thousandths place:
[tex]\[ s \approx 58.524 \][/tex]

### Step 3: Calculate the Direction of the Resultant Vector

The direction [tex]\(\theta\)[/tex] of the resultant vector is found using the arctangent function:
[tex]\[ \theta = \arctan\left(\frac{v_{\text{total}, j}}{v_{\text{total}, i}}\right) \][/tex]

Substituting the values:

[tex]\[ \theta = \arctan\left(\frac{17}{-56}\right) \][/tex]

Since the [tex]\(i\)[/tex]-component (denominator) is negative and the [tex]\(j\)[/tex]-component (numerator) is positive, the direction is in the second quadrant. We must add 180 degrees to our result to get the correct angle direction in standard position:

[tex]\[ \theta = \arctan\left(\frac{17}{-56}\right) + 180^\circ \][/tex]

Calculating the arctangent and converting to degrees:
[tex]\[ \theta \approx -17.00^\circ + 180^\circ \][/tex]
[tex]\[ \theta \approx 163^\circ \][/tex]

Rounding to the nearest degree, we get 163 degrees.

### Step 4: Conclusion

The true speed of the object is [tex]\(58.524\)[/tex] and the direction is [tex]\(163^\circ\)[/tex]. Thus, the correct answer is:

[tex]\[ \boxed{58.524 ; 163^\circ} \][/tex]