A particle of mass m, charge `q gt 0` and initial kinetic energy K is projected from infinity towards a heavy nucleus of charge Q assumed to have a fixed position.
(a) If the aim is perfect, how close to the centre of the nucleus is the particle when it comes instantaneously to rest ?
(b) With a particular imperfect aim, the particle's closest approach to nucleus is twicw the distance determined in (a). Determine speed of particle at the closest distance of approach.

Answer

`(Qq)/(4piepsilon_0K)`