There exists a uniform magnetic and electric field of  magnitude 1 T and 1 V /m, respectively, along positive y-axis. A charged particle of mass 1 kg and of charge 1 C is having velocity 1 m/s along x-axis and is at origin at t = 0. Then the co-ordinates of particle at $\mathrm{time}-\mathrm{\pi }$ seconds will be

The particle will move in a non-uniform helical path with increasing pitch as shown below.

Its time period will be: $\mathrm{T}=\frac{2\mathrm{\pi m}}{\mathrm{qB}}=2\mathrm{\pi }\mathrm{seconds}$

Changing the view, the particle is seemed to move in a circular path in (X - Z) plane as shown below

After $\pi$-seconds the particle will be at point 'P' (after completing half circle), hence X coordinate of P will be 0.

$\begin{array}{l}\mathrm{y}\left(\mathrm{\pi }\right)=0\left(\mathrm{\pi }\right)+\frac{1}{2}\frac{\mathrm{Eq}}{\mathrm{m}}{\left(\mathrm{\pi }\right)}^2=\frac{{\mathrm{\pi }}^2}{2}\\ \mathrm{z}=2\mathrm{r}=2\mathrm{mv}/\mathrm{qB}=2\mathrm{m}\\ \mathrm{Hence},\mathrm{the}\mathrm{coordinate}\left(0,\frac{{\mathrm{\pi }}^2}{2},2\right)\end{array}$