Question

Three point-like charges are placed at the corners of a rectangle as shown in the figure, a = 28.0 cm and b = 54.0 cm. Find the magnitude of the electric force exerted on the charge q1. Let q1 = +1.50 µC, q2 = +3.90 µC, q3 = +3.20 µC.

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Answer 1

F12 = k q1 q2 / b^2

F12 = 9*10^9* 1.5*3.9*10^-12 / 0.54^2

F12 = 0.1806 N

F13 = k q1 q3 / (a^2 + b^2)

F13 = 9*10^9* 1.5* 3.2*10^-12 / (0.28^2 + 0.54^2)

F13=0.117 N

Angle between the forces F13 and F12

x = arctan ( a/ b) = arctan ( 28/54)

x = 27.41

NEt force magnitude on q1

F^2 = F12^2 + F13^2 + 2 F12* F13 cos x

F = 0.2895 N

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