A) \[\frac{10\,m}{3\,q}\]
B) \[\frac{7\,m}{2\,q}\]
C) \[\frac{3\,m}{4\,q}\]
D) \[\frac{4\,m}{3\,q}\]
E) \[\frac{8\,m}{7\,q}\]
Correct Answer: A
Solution :
As force F = qE \[\Rightarrow \] \[ma=qE\Rightarrow a=\frac{qE}{m}\] Similarly, u = 0 The distance covered in time t = 2 s \[{{s}_{1}}=ut+\frac{1}{2}a{{t}^{2}}=0+\frac{1}{2}\frac{qE}{m}\times {{2}^{2}}\] \[=\frac{2qE}{m}\] Now, distance covered at in time t = 1 s \[{{s}_{2}}=\frac{1}{2}\times \frac{qE}{m}\times {{1}^{2}}=\frac{qE}{2m}\] \[\Rightarrow \] \[{{s}_{2}}-{{s}_{1}}=\frac{2qE}{m}-\frac{qE}{2m}\] \[\Rightarrow \] \[s=\frac{qE}{m}\left( 2-\frac{1}{2} \right)\] \[\Rightarrow \] \[E=\frac{10\,m}{3q}\]
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