question_answer

An oil drop having a mass \[4.8\times {{10}^{-10}}g\] and charge \[24\times {{10}^{-18}}C\] stands still between two charged horizontal plates separated by a distance of\[1\,\,cm\]. If now the polarity of the plates is changed, instantaneous acceleration of the drop is\[(g=10\,\,m{{s}^{-2}})\]

A) \[5\,\,m{{s}^{-2}}\]                        

B) \[10\,\,m{{s}^{-2}}\]

C) \[15\,\,m{{s}^{-2}}\]                      

D) \[20\,\,m{{s}^{-2}}\]

Correct Answer: B

Solution :

                \[a=\frac{F}{m}\]                 \[=\frac{qE}{m}\]                 \[=\frac{mg}{m}\]            \[g=10\,\,m/{{s}^{2}}\]