Math Problem Statement

In the sum A + B = C, vector A has a magnitude of 12.0 m and is angled 40° counterclockwise from the +x direction, and vector C has magnitude of 15.0 m and is angled 20° counterclockwise from the −x direction. What are (a) the magnitude and (b) the angle (relative to +x) of B?

Solution

To solve for the magnitude and direction of vector B in the equation A + B = C, we need to use vector components and trigonometry. Here's the step-by-step process:

Given:

  • Magnitude of A: A=12.0m|A| = 12.0 \, \text{m}
  • Direction of A: 4040^\circ counterclockwise from the +x+x-axis.
  • Magnitude of C: C=15.0m|C| = 15.0 \, \text{m}
  • Direction of C: 2020^\circ counterclockwise from the x-x-axis (this is equivalent to 18020=160180^\circ - 20^\circ = 160^\circ relative to the +x+x-axis).

Step 1: Find the components of vectors A and C.

We can break down vectors A and C into their x and y components using trigonometry.

For vector A:

  • Ax=Acos(40)=12.0cos(40)A_x = |A| \cdot \cos(40^\circ) = 12.0 \cdot \cos(40^\circ)
  • Ay=Asin(40)=12.0sin(40)A_y = |A| \cdot \sin(40^\circ) = 12.0 \cdot \sin(40^\circ)

For vector C:

  • Cx=Ccos(160)=15.0cos(160)C_x = |C| \cdot \cos(160^\circ) = 15.0 \cdot \cos(160^\circ)
  • Cy=Csin(160)=15.0sin(160)C_y = |C| \cdot \sin(160^\circ) = 15.0 \cdot \sin(160^\circ)

Step 2: Calculate components of vector B.

Since A+B=C\mathbf{A} + \mathbf{B} = \mathbf{C}, we have:

  • Bx=CxAxB_x = C_x - A_x
  • By=CyAyB_y = C_y - A_y

Step 3: Calculate the magnitude and direction of vector B.

  • Magnitude of B: B=Bx2+By2|B| = \sqrt{B_x^2 + B_y^2}
  • Angle of B relative to the +x+x-axis: θB=tan1(ByBx)\theta_B = \tan^{-1} \left( \frac{B_y}{B_x} \right)

Let's compute these values.import math

Given values

A_magnitude = 12.0 # magnitude of A in meters A_angle = 40 # angle of A in degrees relative to +x axis C_magnitude = 15.0 # magnitude of C in meters C_angle = 160 # angle of C in degrees relative to +x axis

Convert angles to radians for trigonometric calculations

A_angle_rad = math.radians(A_angle) C_angle_rad = math.radians(C_angle)

Components of vector A

A_x = A_magnitude * math.cos(A_angle_rad) A_y = A_magnitude * math.sin(A_angle_rad)

Components of vector C

C_x = C_magnitude * math.cos(C_angle_rad) C_y = C_magnitude * math.sin(C_angle_rad)

Components of vector B (B_x = C_x - A_x, B_y = C_y - A_y)

B_x = C_x - A_x B_y = C_y - A_y

Magnitude of vector B

B_magnitude = math.sqrt(B_x2 + B_y2)

Angle of vector B relative to +x axis (in degrees)

B_angle = math.degrees(math.atan2(B_y, B_x))

B_magnitude, B_angleThe magnitude and angle of vector B are as follows:

  • Magnitude of B: 23.43m23.43 \, \text{m}
  • Angle of B relative to the +x+x-axis: 173.67-173.67^\circ (which means it is slightly below the negative xx-axis).

Would you like more details or clarifications?

Here are some related questions for further practice:

  1. How would the magnitude of vector B change if vector C was doubled?
  2. What happens to the angle of vector B if the angle of C is reduced by 30 degrees?
  3. How would you approach this problem if vector A was vertical instead of angled?
  4. What is the direction of vector A + B if vector C was rotated 90 degrees?
  5. How do you convert between Cartesian and polar coordinates in vector problems?

Tip: Always check the quadrant in which a vector lies when calculating the angle to avoid sign errors in trigonometric functions.

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Math Problem Analysis

Mathematical Concepts

Vectors
Trigonometry

Formulas

Vector addition using components
Magnitude of a vector
Direction of a vector using trigonometry

Theorems

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Suitable Grade Level

Grades 11-12