Question

ABC is an equilateral triangle of side 0.03 charges of +5 nc +3 nc and -5nc are placed at corners A B C respectively find the resultant force on charge placed at B

Answer 1

Force between charge A and B, FAB= -0.015k N

Force between charge A and C, FAC = -0.015k N

=> FAB = FAC = F

=> Resultant force, F' = [2F2 + 2F2cos 60]1/2 = 0.025k

Force between A and M be F''

Now the forces must be equal in magnitude and opposite in direction for A to be in equilibrium.

=> F' = F''

Distance between A and M, AM = 10[3]1/2

=> k 2Q/300 = 0.025k

=> Q = 3.89 microcoloumb

Therefore, a positive charge should be kept at the mid poiny of BC for charge A to be in equilibrium.