b
કાર્ય \({\text{W}}\,\, = \,\,\frac{{\text{1}}}{{\text{2}}}\,m{\upsilon ^2}\, = \,\,q\,\,V\,\,\,\,\therefore \,\,\upsilon \,\, = \,\,\,\sqrt {\frac{{2q\,\,V}}{m}} \,\,\,\,\)

\(\therefore \,\,\frac{{{\upsilon _A}}}{{{\upsilon _B}}}\,\, = \,\,\sqrt {\frac{{{q_A}}}{{{q_B}}}} \,\,\, = \,\,\,\sqrt {\frac{q}{{4q}}} \,\, = \,\,\frac{1}{2}\,\,\,\,\therefore \,\,\frac{{{\upsilon _A}}}{{{\upsilon _B}}}\,\,\, = \,\,1\,\,:\,\,2\)