Math Problem Statement

Find the magnitudes of velocities v_A and v_B in the figure below, where θ = 23.0° and v_tot = 5.56 m/s.

Solution

The image you provided shows a vector addition problem where you need to find the magnitudes of two velocities, vAv_A and vBv_B, given that their resultant vtot=vA+vBv_{\text{tot}} = v_A + v_B, forms specific angles with respect to the x and y axes.

Here’s how to approach the problem:

Given:

  • θ=23.0\theta = 23.0^\circ (the angle between the resultant vector vtotv_{\text{tot}} and the y-axis),
  • ϕ=26.5\phi = 26.5^\circ (the angle between vAv_A and the x-axis),
  • vtot=5.56m/sv_{\text{tot}} = 5.56 \, \text{m/s} (magnitude of the resultant velocity).

Step 1: Resolve the components of the velocities

We can resolve the vectors using trigonometry. From the triangle:

  1. vAv_A has a known angle 26.526.5^\circ with the x-axis, so:

    • vAcos(26.5)v_A \cos(26.5^\circ) is the x-component of vAv_A,
    • vAsin(26.5)v_A \sin(26.5^\circ) is the y-component of vAv_A.
  2. vtotv_{\text{tot}} is the resultant vector, and its components are:

    • vtotsin(23.0)v_{\text{tot}} \sin(23.0^\circ) is the x-component of vtotv_{\text{tot}},
    • vtotcos(23.0)v_{\text{tot}} \cos(23.0^\circ) is the y-component of vtotv_{\text{tot}}.

Step 2: Set up the equations

The total velocity vtotv_{\text{tot}} is the sum of the components of vAv_A and vBv_B. Thus, we can write the equations for the x and y components as:

  1. For the x-component: vAcos(26.5)=vtotsin(23.0)v_A \cos(26.5^\circ) = v_{\text{tot}} \sin(23.0^\circ)

  2. For the y-component: vAsin(26.5)+vB=vtotcos(23.0)v_A \sin(26.5^\circ) + v_B = v_{\text{tot}} \cos(23.0^\circ)

Step 3: Solve for vAv_A and vBv_B

We can solve these two equations to find the magnitudes of vAv_A and vBv_B.

  1. From the first equation: vA=vtotsin(23.0)cos(26.5)v_A = \frac{v_{\text{tot}} \sin(23.0^\circ)}{\cos(26.5^\circ)}

    Plugging in the values: vA=5.56×sin(23.0)cos(26.5)v_A = \frac{5.56 \times \sin(23.0^\circ)}{\cos(26.5^\circ)} vA2.27m/sv_A \approx 2.27 \, \text{m/s}

  2. Now, substitute vAv_A into the second equation to find vBv_B: vAsin(26.5)+vB=vtotcos(23.0)v_A \sin(26.5^\circ) + v_B = v_{\text{tot}} \cos(23.0^\circ) 2.27×sin(26.5)+vB=5.56×cos(23.0)2.27 \times \sin(26.5^\circ) + v_B = 5.56 \times \cos(23.0^\circ) Solving for vBv_B: vB=5.56×cos(23.0)2.27×sin(26.5)v_B = 5.56 \times \cos(23.0^\circ) - 2.27 \times \sin(26.5^\circ) vB4.99m/sv_B \approx 4.99 \, \text{m/s}

Final Answer:

  • vA2.27m/sv_A \approx 2.27 \, \text{m/s}
  • vB4.99m/sv_B \approx 4.99 \, \text{m/s}

Would you like further clarification or more details on this solution?


Here are 5 related questions to expand on this concept:

  1. How do you decompose any vector into its x and y components?
  2. What would happen to the solution if the angle between vAv_A and the x-axis changed?
  3. How can you use the law of cosines to solve similar vector problems?
  4. What is the geometric interpretation of vector addition?
  5. How would you apply this method to find the relative velocities in a moving frame?

Tip: Always double-check the units and angles when working with trigonometric identities in physics problems to avoid calculation errors!

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Math Problem Analysis

Mathematical Concepts

Vector Addition
Trigonometry

Formulas

v_A * cos(26.5°) = v_tot * sin(23.0°)
v_A * sin(26.5°) + v_B = v_tot * cos(23.0°)

Theorems

Trigonometric Identities
Vector Decomposition

Suitable Grade Level

Grades 10-12