Math Problem Statement

Vector A is 2 in. long and is 60° above the x-axis in the first quadrant. Vector B is 2 in. long and is 60° below the x-axis in the fourth quadrant. Find graphically: a) the vector sum A + B, and b) the vector differences A - B and B - A.

Solution

The problem describes two vectors A\mathbf{A} and B\mathbf{B} as follows:

  • Vector A\mathbf{A}:

    • Magnitude: 2 inches.
    • Direction: 6060^\circ above the x-axis (in the first quadrant).
  • Vector B\mathbf{B}:

    • Magnitude: 2 inches.
    • Direction: 6060^\circ below the x-axis (in the fourth quadrant).

You are asked to find graphically:

  1. The vector sum A+B\mathbf{A} + \mathbf{B}.
  2. The vector differences AB\mathbf{A} - \mathbf{B} and BA\mathbf{B} - \mathbf{A}.

Solution Breakdown:

We can break down each vector into its components and then use vector addition/subtraction principles. The graphical method would also involve these components.

1. Components of Vector A\mathbf{A}:

Since A\mathbf{A} is 60° above the x-axis in the first quadrant, its components are:

  • Ax=Acos(60)=2×12=1A_x = A \cos(60^\circ) = 2 \times \frac{1}{2} = 1 inch (positive x-component).
  • Ay=Asin(60)=2×32=3A_y = A \sin(60^\circ) = 2 \times \frac{\sqrt{3}}{2} = \sqrt{3} inches (positive y-component).

Thus, A=(1,3)\mathbf{A} = (1, \sqrt{3}) inches.

2. Components of Vector B\mathbf{B}:

Since B\mathbf{B} is 60° below the x-axis in the fourth quadrant, its components are:

  • Bx=Bcos(60)=2×12=1B_x = B \cos(60^\circ) = 2 \times \frac{1}{2} = 1 inch (positive x-component).
  • By=Bsin(60)=2×32=3B_y = B \sin(60^\circ) = 2 \times \frac{\sqrt{3}}{2} = \sqrt{3} inches (negative y-component).

Thus, B=(1,3)\mathbf{B} = (1, -\sqrt{3}) inches.

a) Vector Sum A+B\mathbf{A} + \mathbf{B}:

Adding the components:

  • (A+B)x=1+1=2(\mathbf{A} + \mathbf{B})_x = 1 + 1 = 2 inches.
  • (A+B)y=3+(3)=0(\mathbf{A} + \mathbf{B})_y = \sqrt{3} + (-\sqrt{3}) = 0 inches.

Thus, A+B=(2,0)\mathbf{A} + \mathbf{B} = (2, 0) inches, which is a vector of magnitude 2 inches along the x-axis.

b) Vector Differences AB\mathbf{A} - \mathbf{B} and BA\mathbf{B} - \mathbf{A}:

  1. AB\mathbf{A} - \mathbf{B}: Subtracting the components:

    • (AB)x=11=0(\mathbf{A} - \mathbf{B})_x = 1 - 1 = 0 inches.
    • (AB)y=3(3)=23(\mathbf{A} - \mathbf{B})_y = \sqrt{3} - (-\sqrt{3}) = 2\sqrt{3} inches.

    Thus, AB=(0,23)\mathbf{A} - \mathbf{B} = (0, 2\sqrt{3}) inches, which is a vertical vector of magnitude 232\sqrt{3} inches.

  2. BA\mathbf{B} - \mathbf{A}: Subtracting the components:

    • (BA)x=11=0(\mathbf{B} - \mathbf{A})_x = 1 - 1 = 0 inches.
    • (BA)y=33=23(\mathbf{B} - \mathbf{A})_y = -\sqrt{3} - \sqrt{3} = -2\sqrt{3} inches.

    Thus, BA=(0,23)\mathbf{B} - \mathbf{A} = (0, -2\sqrt{3}) inches, which is a vertical vector in the negative y-direction with magnitude 232\sqrt{3} inches.

Summary:

  • A+B=(2,0)\mathbf{A} + \mathbf{B} = (2, 0) inches.
  • AB=(0,23)\mathbf{A} - \mathbf{B} = (0, 2\sqrt{3}) inches.
  • BA=(0,23)\mathbf{B} - \mathbf{A} = (0, -2\sqrt{3}) inches.

Would you like further details or have any questions?

Related Questions:

  1. What is the general process to find the magnitude and direction of a vector?
  2. How does vector subtraction differ from vector addition graphically?
  3. What are the differences between first quadrant and fourth quadrant vectors?
  4. How would changing the angle of vectors A\mathbf{A} or B\mathbf{B} affect the resultant sum?
  5. Can you solve vector addition problems using trigonometry instead of graphical methods?

Tip:

Always ensure that you correctly account for the signs of vector components based on their direction in the coordinate plane.

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Math Problem Analysis

Mathematical Concepts

Vector Addition
Vector Subtraction
Trigonometry

Formulas

Ax = A * cos(θ)
Ay = A * sin(θ)
Bx = B * cos(θ)
By = B * sin(θ)
A + B = (Ax + Bx, Ay + By)
A - B = (Ax - Bx, Ay - By)

Theorems

Pythagorean Theorem for vector magnitude
Law of Sines and Cosines for vector components

Suitable Grade Level

Grades 10-12