Two fixed, equal, positive charges, each of magnitude `5xx10^-5` coul are located at points A and B separated by a distance of 6m. An equal and opposite charge moves towards them along the line COD, the perpendicular bisector of the line AB.
The moving charge, when it reaches the point C at a distance of 4m from O, has a kinetic energy of 4 joules. Calculate the distance of the farthest point D which the negative charge will reach before returning towards C.

Answer

B

Explanation

From energy conservation
`U_C+K_C=U_D+K_D`
`or 2[(9xx10^9xx(5xx10^-5)(-5xx10^-5))/5]+4`
`=2 [((9xx10^9x(5xx10^-5)(-5x10^-5))/(AD)]+0`
solving we get `AD =9m`
`:.` maximum distance
`OD=sqrt((9)^2-(3)^2`
`=sqrt72m`