A charge particle of charge q, mass m is moving with initial velocity ‘v’ as shown in figure in a uniform magnetic field $-\mathrm{B}\widehat{\mathrm{k}}$. Select the correct alternative/alternatives:-

Inside the magnetic field the trajectory of the particle will be a cicular arc which is concave upward .So y - component of its velocity is positive , Hence option  (1) is wrong .

The centre of curvature of the arc lies on the y - axis and the arc subtends an angle of $\frac{\mathrm{\pi }}{3}, at the centre of curvature .$

$\mathrm{ArcAB}=\frac{\mathrm{\pi }}{3}\mathrm{r}=\frac{\mathrm{\pi mV}}{3\mathrm{qB}}\text{ Time ' }\mathrm{t}\text{ ' }$

$=\left(\frac{1}{2\mathrm{\pi }}\right)\left(\frac{\mathrm{\pi }}{3}\right)=\frac{\mathrm{T}}{6}=\frac{\mathrm{\pi m}}{3\mathrm{qB}}$