The total electric force that these charges exert on a third point charge is 11.9 N and the direction is towards positive y axis.
The force between the first charge and the third charge is calculated as follows;
F₁₃ = kq₁q₃/r₁₃²
F₁₃ = (9 x 10⁹ x 3 x 10⁻⁶ x 4.5 x 10⁻⁶) / (0.1)²
note: distance between charge 3.0 μC and Q = 4.5 μC = 0.4 m - 0.3 m = 0.1 m
F₁₃ = 12.15 N
The force between the second charge and the third charge is calculated as follows;
F₂₃ = kq₂q₃/r₂₃²
F₂₃ = (9 x 10⁹ x -3 x 10⁻⁶ x 4.5 x 10⁻⁶) / (0.7)²
note: distance between charge -3.0 μC and Q = 4.5 μC = 0.4 m - (-0.3 m) = 0.7 m
F₂₃ = -0.248 N
F(net) = F₁₃ + F₂₃
F(net) = 12.15 - 0.248
F(net) = 11.9 N
Thus, the total electric force that these charges exert on a third point charge is 11.9 N and the direction is towards positive y axis.
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