The space has electromagnetic field which varies with time whose variation is given as:

$\overrightarrow{B}=\{\begin{array}{ccc}-B_0\widehat{k}& if& 0\le t\le \frac{\pi m}{q{B}_0}\\ -B_0\widehat{j}& if& \frac{\pi m}{q{B}_0}\le t\le \frac{2\pi m}{q{B}_0}\\ 0& if& \frac{2\pi m}{q{B}_0}\le t<\infty \end{array} and \overrightarrow{E}=\{\begin{array}{ccc}0& if& 0\le t\le \frac{2\pi m}{q{B}_0}\\ -E_0\widehat{k}& if& \frac{2\pi m}{q{B}_0}\le t<\infty \end{array}$

 

A charge particle having mass m and positive charge q is given a velocity $v_0\widehat{i}$ at origin at t = 0. The coordinates of the point on xy plane where it again passes through the xy plane for the first time are $\left(\frac{Km{v}_0}{q}\sqrt{\frac{v_0}{E_0{B}_0}},\frac{2m{v}_0}{Nq{B}_0},0\right)$