Two protons are projected simultaneously from a fixed point with the same velocity $v$ with a region where there exists a uniform magnetic field . The magnetic field strength is $B$, and is perpendicular to the initial direction of $v$. One proton starts at time $t=0$ and another proton at time $t=\frac{\mathrm{\pi m}}{2qB}$. The separation between them at time $t=\frac{\mathrm{\pi m}}{qB}$[where $m$ and $q$ are the mass and charge of proton], will approximately (neglect electrostatic force between protons)