Math Problem Statement

Vector  B→B→ has magnitude 7.30 and direction 14.0° below the +x-axis. Vector  C→C→ has x-component Cx = −1.90 and y-component Cy = −6.70.  

What angle does the resultant vector  C→+B→C→+B→  make with the +x-axis in clockwise direction? A positive angle is counterclockwise from the +x-axis.

Solution

To find the angle that the resultant vector R=C+B\vec{R} = \vec{C} + \vec{B} makes with the +x+x-axis in the clockwise direction, follow these steps:

Step 1: Determine the components of vector B\vec{B}

Given:

  • Magnitude of B\vec{B}: B=7.30B = 7.30
  • Direction of B\vec{B}: 14.014.0^\circ below the +x+x-axis

Since 14.014.0^\circ is below the +x+x-axis, it’s equivalent to 14.0-14.0^\circ when measured counterclockwise from the +x+x-axis.

The components of B\vec{B} are: Bx=Bcos(14.0)andBy=Bsin(14.0)B_x = B \cos(-14.0^\circ) \quad \text{and} \quad B_y = B \sin(-14.0^\circ)

Substituting the values: Bx=7.30cos(14.0)7.08(rounded to two decimal places)B_x = 7.30 \cos(-14.0^\circ) \approx 7.08 \quad \text{(rounded to two decimal places)} By=7.30sin(14.0)1.77(rounded to two decimal places)B_y = 7.30 \sin(-14.0^\circ) \approx -1.77 \quad \text{(rounded to two decimal places)}

Step 2: Combine the components of B\vec{B} and C\vec{C}

Given for vector C\vec{C}:

  • Cx=1.90C_x = -1.90
  • Cy=6.70C_y = -6.70

The components of the resultant vector R=C+B\vec{R} = \vec{C} + \vec{B} are: Rx=Cx+Bx=1.90+7.08=5.18R_x = C_x + B_x = -1.90 + 7.08 = 5.18 Ry=Cy+By=6.70+(1.77)=8.47R_y = C_y + B_y = -6.70 + (-1.77) = -8.47

Step 3: Calculate the angle of the resultant vector

The angle θR\theta_R that the resultant vector makes with the +x+x-axis is given by: θR=tan1(RyRx)\theta_R = \tan^{-1}\left(\frac{R_y}{R_x}\right) Substituting the values: θR=tan1(8.475.18)\theta_R = \tan^{-1}\left(\frac{-8.47}{5.18}\right) θRtan1(1.635)58.84\theta_R \approx \tan^{-1}(-1.635) \approx -58.84^\circ

Step 4: Interpret the angle in the clockwise direction

The angle 58.84-58.84^\circ is measured counterclockwise from the +x+x-axis, which corresponds to 58.8458.84^\circ clockwise. Therefore, the angle in the clockwise direction is:

θclockwise=58.84\theta_{\text{clockwise}} = 58.84^\circ

So, the resultant vector C+B\vec{C} + \vec{B} makes an angle of approximately 58.8458.84^\circ clockwise from the +x+x-axis.

Would you like any further explanation or details? Here are some related questions you might find interesting:

  1. How do you calculate the magnitude of the resultant vector R\vec{R}?
  2. Why is the direction below the +x+x-axis considered as a negative angle?
  3. How would the situation change if the vectors were in three dimensions?
  4. What are the trigonometric identities used in calculating vector components?
  5. How would you approach this problem if the angle for B\vec{B} were given above the +x+x-axis?

Tip: When dealing with angles and vector components, always ensure the angle is measured with respect to the correct axis, and consider the sign (positive or negative) of the components based on the vector's direction.

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Math Problem Analysis

Mathematical Concepts

Vectors
Trigonometry

Formulas

Vector addition components
Angle calculation using trigonometry

Theorems

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Suitable Grade Level

High School