Solution

A positively charged particle is projected perpendicularly into a magnetic field at a speed of $1500\,\mathrm{m\,s^{-1}}$. It experiences a force of magnitude $F$. At what angle $\theta$ with the field, the particle should be projected at a speed of $2000\,\mathrm{m\,s^{-1}}$, so that it experiences the same magnitude of force?