question_answer

A oil drop having a mass \[4.8\times {{10}^{-10}}g\] and charge \[2.4\times {{10}^{-18}}\text{ }C\] stands still between two charged horizontal plates separated by 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 :

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