# A charge particle of mass 1 kg and charge $1 \mu c$ is projected from horizontal ground at an angle $\theta=45^{\circ}$ with speed $10 ms^{-1}$. In space a horizontal electric field towards the direction of projection $E= 10^{7}NC^{-1}$ exists. The range of projectile is :

$(A)\;200 m \\ (B)\;20 m \\ (C)\;60 m \\ (D)\;300 m$

$a_x =\large\frac{qE}{m}=\large\frac{1 \times 10^{-6} \times 10^7}{1}$
$\qquad =10\;ms^{-2}$
Time of flight $t= \large\frac{2 u \sin \theta}{g}$
=> $t= \large\frac{2 \times 10}{10} \times \large\frac{1}{\sqrt 2}$
=> $\quad= \sqrt 2 sec$
$Range = U \times t +\large\frac{1}{2} $$a \times t^2 \qquad= 10 \times \large\frac{1}{\sqrt 2}$$ \times \sqrt 2 +\large\frac{1}{2}$$\times 10 \times (\sqrt 2)^2$
$\qquad= 20 m$
Hence B is the correct answer.