Math Problem Statement

The three displacement vectors are A going to the +y axis and - x axis, B going to the +y and +x axis, and C going straight down on the -y axis. They have a magnitude of A=5.4m, B=5.14m, and C=3.45m. Find the resultant (a) magnitude and (b) directional angle of the three vectors by means of the component method. Express the directional angle as an angle above the positive or negative x axis which is less than 90 degrees.

Solution

To find the resultant vector of the three displacement vectors A\mathbf{A}, B\mathbf{B}, and C\mathbf{C} using the component method, we need to break down each vector into its components along the x and y axes, then sum up the components to get the resultant vector's components. Finally, we can calculate the magnitude and direction of the resultant vector.

1. Breaking down the vectors into components:

Vector A\mathbf{A}:

  • A\mathbf{A} has a magnitude of 5.4 m, and it points in the positive y direction and negative x direction. Thus, we can write:
    • Ax=5.4mA_x = -5.4 \, \text{m} (negative because it points in the negative x direction)
    • Ay=5.4mA_y = 5.4 \, \text{m} (positive because it points in the positive y direction)

Vector B\mathbf{B}:

  • B\mathbf{B} has a magnitude of 5.14 m, and it points in the positive y direction and positive x direction. Thus, we can write:
    • Bx=5.14mB_x = 5.14 \, \text{m} (positive because it points in the positive x direction)
    • By=5.14mB_y = 5.14 \, \text{m} (positive because it points in the positive y direction)

Vector C\mathbf{C}:

  • C\mathbf{C} has a magnitude of 3.45 m, and it points directly downward along the negative y axis. Thus, we can write:
    • Cx=0mC_x = 0 \, \text{m} (no x component because it points vertically)
    • Cy=3.45mC_y = -3.45 \, \text{m} (negative because it points in the negative y direction)

2. Summing the components:

Now, we sum the x and y components of all three vectors:

x-components of the resultant vector:

Rx=Ax+Bx+Cx=5.4+5.14+0=0.26mR_x = A_x + B_x + C_x = -5.4 + 5.14 + 0 = -0.26 \, \text{m}

y-components of the resultant vector:

Ry=Ay+By+Cy=5.4+5.143.45=7.09mR_y = A_y + B_y + C_y = 5.4 + 5.14 - 3.45 = 7.09 \, \text{m}

3. Calculating the magnitude of the resultant vector:

The magnitude of the resultant vector R\mathbf{R} is given by: R=Rx2+Ry2=(0.26)2+(7.09)2=0.0676+50.4081=50.47577.11mR = \sqrt{R_x^2 + R_y^2} = \sqrt{(-0.26)^2 + (7.09)^2} = \sqrt{0.0676 + 50.4081} = \sqrt{50.4757} \approx 7.11 \, \text{m}

4. Calculating the directional angle of the resultant vector:

The direction θ\theta of the resultant vector relative to the positive x-axis is given by: θ=tan1(RyRx)\theta = \tan^{-1} \left( \frac{R_y}{R_x} \right) Since RxR_x is negative and RyR_y is positive, the resultant vector is in the second quadrant, and we can compute: θ=tan1(7.090.26)=tan1(27.27)\theta = \tan^{-1} \left( \frac{7.09}{-0.26} \right) = \tan^{-1}(-27.27) This gives an angle of approximately: θ88.4\theta \approx -88.4^\circ Since we need an angle above the positive or negative x-axis, we convert this to a positive angle in the second quadrant: θ=18088.4=91.6\theta = 180^\circ - 88.4^\circ = 91.6^\circ Thus, the angle is approximately 91.691.6^\circ above the negative x-axis.

Final Answer:

  • (a) The magnitude of the resultant vector is approximately 7.11 m.
  • (b) The directional angle of the resultant vector is approximately 91.6° above the negative x-axis.

Would you like further clarification or details on any part of this solution?

Here are some related questions you might find interesting:

  1. How do you break vectors into components in 3D space?
  2. What are some methods to find the direction of a vector in physics?
  3. How can the dot product be used to find angles between vectors?
  4. What is the difference between vector addition in Cartesian and polar coordinates?
  5. Can you solve for the resultant when vectors have both x, y, and z components?

Tip: When dealing with vector components, always ensure you correctly handle signs and directions, especially when the vectors are in different quadrants!

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Math Problem Analysis

Mathematical Concepts

Vector Addition
Component Method
Trigonometry
Magnitude of a Vector
Direction of a Vector

Formulas

R = sqrt(R_x^2 + R_y^2)
theta = tan^-1(R_y / R_x)

Theorems

Pythagorean Theorem
Arctangent Function

Suitable Grade Level

Grades 10-12