S-I: A proton and an alpha particle having the same kinetic energy are moving in circular paths in a uniform magnetic field. The radii of their circular paths will be equal. <br> S-II: Any two charged particles having same kinetic energy are moving an circular paths in a uniform magnetic field $\vec{B}$ in a direction perpendicular to $\overrightarrow{\mathrm{B}}$, will describe circular trajectories of equal radii.