Three point charges of +2 microcoulomb,-3 microcoulomb and -3 microcoulomb are kept at the vertices A,B and C respectively of - Physics - Electric Charges And Fields

Question

Three point charges of +2 microcoulomb,-3 microcoulomb and -3
microcoulomb are kept at the vertices A,B and C respectively of an
equilateral triangle of side 20 cm What should be the sign and
magnitude of the charge to be placed at the mid point(M) of side BC
so that the charge at A remains in equilibrium?

Panchali Dutta · Accepted Answer

<img alt="" src=
"https://s3mn%20mnimgs%20com/img/shared/discuss_editlive/3079860/2012_07_13_16_55_39/chargeandequilateraltriangle_572519508306298499%20jpg">
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
@ somya: good work keep posting!