Math Problem Statement

(Figure 1) shows four electrical charges located at the corners of a rectangle. Like charges, you will recall, repel each other while opposite charges attract. Charge B exerts a repulsive force (directly away from B ) on charge A of 3.3 N . Charge C exerts an attractive force (directly toward C ) on charge A of 6.6 N . Finally, charge D exerts an attractive force of 2.2 N on charge A . Figure1 of 1 Four charged particles are labeled from 'A' to D and placed in the vertices of a rectangle. Charges 'A' and B are positive, charges C and D are negative. Horizontal sides 'A' B and C D have a length of 141 centimeters. Vertical sides 'A' C and B C have a length of 100 centimeters. What is the direction of the net force F⃗ net exerted on charge A ? Use the xy -plane with the origin at A and with x -axis directed to B . Express your answer in degrees measured clockwise from the negative y -axis.

Solution

To determine the direction of the net force Fnet\mathbf{F}_{\text{net}} on charge AA, we'll break down the problem into the following steps:

  1. Identify the Forces:

    • The force exerted by charge BB on AA is repulsive and acts directly to the right (along the positive xx-axis). Let's denote this force as FB=3.3N\mathbf{F}_B = 3.3 \, \text{N}.
    • The force exerted by charge CC on AA is attractive and acts directly downward (along the negative yy-axis). Let's denote this force as FC=6.6N\mathbf{F}_C = 6.6 \, \text{N}.
    • The force exerted by charge DD on AA is attractive and acts diagonally toward DD. Let's denote this force as FD=2.2N\mathbf{F}_D = 2.2 \, \text{N}.
  2. Determine the Components of the Forces:

    • FB\mathbf{F}_B acts entirely along the xx-axis: FB=3.3Ni^\mathbf{F}_B = 3.3 \, \text{N} \, \hat{i}.
    • FC\mathbf{F}_C acts entirely along the yy-axis: FC=6.6Nj^\mathbf{F}_C = -6.6 \, \text{N} \, \hat{j}.
    • FD\mathbf{F}_D has both xx and yy components. The angle between the diagonal ADAD and the horizontal axis can be determined using the dimensions of the rectangle.
  3. Calculate the Angle for Force DD:

    • The length AB=141cmAB = 141 \, \text{cm} and AC=100cmAC = 100 \, \text{cm}.
    • The distance ADAD (the diagonal) can be calculated using the Pythagorean theorem: AD=AB2+AC2=1412+1002=19881+10000174.92cmAD = \sqrt{AB^2 + AC^2} = \sqrt{141^2 + 100^2} = \sqrt{19881 + 10000} \approx 174.92 \, \text{cm}
    • The angle θ\theta between the diagonal ADAD and the horizontal side ABAB is: θ=tan1(ACAB)=tan1(100141)35.1\theta = \tan^{-1}\left(\frac{AC}{AB}\right) = \tan^{-1}\left(\frac{100}{141}\right) \approx 35.1^\circ

    Therefore, the components of FD\mathbf{F}_D are: \mathbf{F}_{Dx} = 2.2 \, \cos(35.1^\circ) \, \text{N} \quad \text{(towards the negative x-axis)} \mathbf{F}_{Dy} = -2.2 \, \sin(35.1^\circ) \, \text{N} \quad \text{(towards the negative y-axis)}

  4. Sum the Components to Find the Net Force:

    • Net force in the xx-direction: Fnet,x=FB+FDx=3.3+2.2×(cos(35.1))3.31.8=1.5NF_{\text{net},x} = F_B + F_{Dx} = 3.3 + 2.2 \times (-\cos(35.1^\circ)) \approx 3.3 - 1.8 = 1.5 \, \text{N}
    • Net force in the yy-direction: Fnet,y=FC+FDy=6.6+2.2×(sin(35.1))6.61.3=7.9NF_{\text{net},y} = F_C + F_{Dy} = -6.6 + 2.2 \times (-\sin(35.1^\circ)) \approx -6.6 - 1.3 = -7.9 \, \text{N}
  5. Determine the Angle of the Net Force:

    • The angle ϕ\phi of the net force from the negative yy-axis can be found using: tan(ϕ)=Fnet,xFnet,y=1.57.90.19\tan(\phi) = \frac{F_{\text{net},x}}{-F_{\text{net},y}} = \frac{1.5}{7.9} \approx 0.19 ϕtan1(0.19)10.7\phi \approx \tan^{-1}(0.19) \approx 10.7^\circ This angle is measured clockwise from the negative yy-axis.

Thus, the direction of the net force on charge AA is approximately 10.7° clockwise from the negative yy-axis.

Would you like more details on this solution? Here are some related questions:

  1. How would the direction change if the magnitude of force CC were reduced?
  2. What if charge DD were moved closer to charge AA?
  3. How does the position of charge BB affect the net force on AA?
  4. What if charges BB and CC were switched?
  5. How would the net force be affected if charge AA were also negative?

Tip: When dealing with forces in multiple directions, always break them into their components and handle each direction separately.

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Math Problem Analysis

Mathematical Concepts

Forces
Vector Components
Pythagorean Theorem
Trigonometry

Formulas

Pythagorean theorem
Vector components
Trigonometric functions

Theorems

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Suitable Grade Level

High School