A bullet of mass m and charge q is fired towards a solid uniformly charge sphere of radius R and total charge +q. If it strikes the surface of sphere with speed u, find the minimum value of u so that it can penetrate through the sphere. (Neglect all resistance force or friction acting on bullet except electrostatic forces)
A. `(q)/(sqrt(2pi epsilon_(0)mR))`
B. `(q)/(sqrt(4pi epsilon_(0)mR))`
C. `(q)/(sqrt(8pi epsilon_(0)mR))`
D. `(sqrt(3)q)/(sqrt(4pi epsilon_(0)mR))`
