Math Problem Statement

Two vectors A and B are shown in the figure (not drawn to scale). Vector A has a magnitude rA = 15 units and an angle θA = 37o. Vector B has a magnitude rB = 40 units and an angle θB of 53o.

Express these vectors in ijk unit vector notation, that is in the form A = Axi + Ayj and B = Bxi + Byj, where Ax, Ay, Bx, and By are the x and y components of vectors A and B, respectively; and find C = A -B. (Magnitude and direction)

Solution

To solve this problem, we'll break it down into a few steps:

Step 1: Express Vectors A and B in Component Form

Given:

  • Vector A\mathbf{A}:
    • Magnitude rA=15r_A = 15 units
    • Angle θA=37\theta_A = 37^\circ
  • Vector B\mathbf{B}:
    • Magnitude rB=40r_B = 40 units
    • Angle θB=53\theta_B = 53^\circ

For a vector V\mathbf{V} with magnitude rVr_V and angle θV\theta_V, the components are given by: Vx=rVcos(θV)V_x = r_V \cos(\theta_V) Vy=rVsin(θV)V_y = r_V \sin(\theta_V)

Vector A Components:

Ax=15cos(37)A_x = 15 \cos(37^\circ) Ay=15sin(37)A_y = 15 \sin(37^\circ)

Vector B Components:

Bx=40cos(53)B_x = 40 \cos(53^\circ) By=40sin(53)B_y = 40 \sin(53^\circ)

Let's calculate these components.

Step 2: Calculate the Components

For Vector A:

Ax=15cos(37)15×0.798611.979A_x = 15 \cos(37^\circ) \approx 15 \times 0.7986 \approx 11.979 Ay=15sin(37)15×0.60189.027A_y = 15 \sin(37^\circ) \approx 15 \times 0.6018 \approx 9.027

So, A\mathbf{A} in component form is: A=11.979i^+9.027j^\mathbf{A} = 11.979\hat{i} + 9.027\hat{j}

For Vector B:

Bx=40cos(53)40×0.601824.072B_x = 40 \cos(53^\circ) \approx 40 \times 0.6018 \approx 24.072 By=40sin(53)40×0.798631.944B_y = 40 \sin(53^\circ) \approx 40 \times 0.7986 \approx 31.944

So, B\mathbf{B} in component form is: B=24.072i^+31.944j^\mathbf{B} = 24.072\hat{i} + 31.944\hat{j}

Step 3: Find Vector C=AB\mathbf{C} = \mathbf{A} - \mathbf{B}

Subtract the components of vector B\mathbf{B} from vector A\mathbf{A}: Cx=AxBx=11.97924.07212.093C_x = A_x - B_x = 11.979 - 24.072 \approx -12.093 Cy=AyBy=9.02731.94422.917C_y = A_y - B_y = 9.027 - 31.944 \approx -22.917

So, vector C\mathbf{C} in component form is: C=12.093i^22.917j^\mathbf{C} = -12.093\hat{i} - 22.917\hat{j}

Step 4: Calculate the Magnitude and Direction of Vector C\mathbf{C}

Magnitude of C\mathbf{C}:

C=Cx2+Cy2=(12.093)2+(22.917)2146.24+525.17671.4125.9 units|\mathbf{C}| = \sqrt{C_x^2 + C_y^2} = \sqrt{(-12.093)^2 + (-22.917)^2} \approx \sqrt{146.24 + 525.17} \approx \sqrt{671.41} \approx 25.9 \text{ units}

Direction of C\mathbf{C} (Angle with the positive x-axis):

θC=tan1(CyCx)=tan1(22.91712.093)tan1(1.895)62.1\theta_C = \tan^{-1}\left(\frac{C_y}{C_x}\right) = \tan^{-1}\left(\frac{-22.917}{-12.093}\right) \approx \tan^{-1}(1.895) \approx 62.1^\circ

Since both CxC_x and CyC_y are negative, θC\theta_C is in the third quadrant. The angle in the third quadrant relative to the positive x-axis is: θC180+62.1=242.1\theta_C \approx 180^\circ + 62.1^\circ = 242.1^\circ

Final Answer:

  • The vectors in component form are: A=11.979i^+9.027j^\mathbf{A} = 11.979\hat{i} + 9.027\hat{j} B=24.072i^+31.944j^\mathbf{B} = 24.072\hat{i} + 31.944\hat{j}
  • The vector C=AB\mathbf{C} = \mathbf{A} - \mathbf{B} has a magnitude of approximately 25.9 units and a direction of 242.1242.1^\circ relative to the positive x-axis.

Would you like more details, or do you have any questions?

Related Questions:

  1. How would you find the vector sum A+B\mathbf{A} + \mathbf{B}?
  2. What is the physical significance of vector subtraction in real-world applications?
  3. How can you express the direction of vector C\mathbf{C} using other trigonometric functions?
  4. How does the change in the angle θA\theta_A or θB\theta_B affect the resultant vector?
  5. Can vector components be negative, and what does that imply about the direction of the vector?

Tip:

Always visualize the vectors and their components on the Cartesian plane to better understand their resultant magnitudes and directions.

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Math Problem Analysis

Mathematical Concepts

Vectors
Component Form
Vector Subtraction
Magnitude of Vectors
Direction of Vectors

Formulas

Vector components using magnitude and angle
Magnitude of a vector
Direction of a vector

Theorems

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Suitable Grade Level

Grades 11-12