Math Problem Statement

Four forces are working against each other (on the same plane, so you don't need to consider three dimensional space). Two of the forces, of magnitudes 70 N and 50 N, act in opposite directions to each other. The other two forces, of magnitudes 20 N and 60 N, act in opposite directions to each other as well. The 20 N force is at an angle of 40° to the 50 N force and the 60 N is at an angle of 40 to the 70 N. Find the resultant force and the equilibrant force.

Solution

To solve this problem, we need to find the resultant of the four forces acting in different directions and then calculate the equilibrant force, which will be equal in magnitude but opposite in direction to the resultant.

Step 1: Break the forces into components

Let's assume the xx-axis is aligned with the 70 N and 50 N forces, and the angles are measured from these axes.

  • The 70 N force acts along the positive xx-axis.

  • The 50 N force acts along the negative xx-axis.

  • The 20 N force is at an angle of 40° with the 50 N force (negative xx-axis). So, its components are: F20x=20cos(40°),F20y=20sin(40°)F_{20x} = 20 \cos(40°), \quad F_{20y} = 20 \sin(40°) Since this force is at 40° from the negative xx-axis, the xx-component will be negative.

  • The 60 N force is at an angle of 40° with the 70 N force (positive xx-axis). So, its components are: F60x=60cos(40°),F60y=60sin(40°)F_{60x} = 60 \cos(40°), \quad F_{60y} = 60 \sin(40°) Since this force is at 40° from the positive xx-axis, both components are positive.

Step 2: Sum the components in the xx- and yy-directions

  1. In the xx-direction: Fx=705020cos(40°)+60cos(40°)F_x = 70 - 50 - 20 \cos(40°) + 60 \cos(40°)

  2. In the yy-direction: Fy=60sin(40°)20sin(40°)F_y = 60 \sin(40°) - 20 \sin(40°)

Step 3: Calculate the magnitudes of components

Let’s calculate these values.

Step 4: Calculate the resultant force magnitude

Once the components FxF_x and FyF_y are known, the resultant force can be found using the Pythagorean theorem: R=Fx2+Fy2R = \sqrt{F_x^2 + F_y^2}

Step 5: Find the direction of the resultant force

The angle θ\theta of the resultant force relative to the xx-axis is: θ=tan1(FyFx)\theta = \tan^{-1} \left(\frac{F_y}{F_x}\right)

Step 6: Calculate the equilibrant force

The equilibrant force will have the same magnitude as the resultant force but will point in the opposite direction. Its angle will be: θequilibrant=θ+180°\theta_{\text{equilibrant}} = \theta + 180°

I will now calculate these values for you.### Result:

  1. The components of the resultant force are:

    • Fx=50.64NF_x = 50.64 \, \text{N}
    • Fy=25.71NF_y = 25.71 \, \text{N}
  2. The magnitude of the resultant force is: R=56.79NR = 56.79 \, \text{N}

  3. The direction of the resultant force is: θres=26.92above the positive x-axis\theta_{\text{res}} = 26.92^\circ \, \text{above the positive x-axis}

  4. The equilibrant force has the same magnitude but acts in the opposite direction: θequilibrant=206.92\theta_{\text{equilibrant}} = 206.92^\circ

Would you like further details on the process, or any additional clarifications?

Here are 5 related questions:

  1. How do you resolve forces at different angles into components?
  2. Why do opposite forces cancel each other in some cases?
  3. How does the direction of the equilibrant force relate to the resultant force?
  4. What role does trigonometry play in calculating force components?
  5. How would the result change if the angles were different?

Tip: Always draw a diagram when working with force vectors to visually represent directions and angles.

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Math Problem Analysis

Mathematical Concepts

Vector Addition
Trigonometry

Formulas

F_x = 70 - 50 - 20 * cos(40°) + 60 * cos(40°)
F_y = 60 * sin(40°) - 20 * sin(40°)
R = sqrt(F_x^2 + F_y^2)
θ = tan^(-1)(F_y / F_x)
θ_equilibrant = θ + 180°

Theorems

Pythagorean Theorem
Trigonometric Functions

Suitable Grade Level

Grades 11-12