Q.
A uniform magnetic field B is acting from south to north and is of magnitude $1.5\ wb/m^{2}$. If a proton having mass $= 1.7 \times 10^{- 27}kg$ and charge $= 1.6 \times 10^{- 19}C$ moves in this field vertically downward with energy $5\ MeV$, then the force acting on it will be