A particle $($mass $=4\mathrm{.}0$ g$,$ charge $=80$ mC$)$ moves in a region of space where the electric field is uniform and is given by Ex $=-2\mathrm{.}5$ N$/$C$,$ Ey $=$ Ez $=$ O$.$ If the velocity of the

particle at t $=0$ is given by vx $=80$ m$/$s$,$ Vy $=$ Vz $=0,$ what is the speed of the particle at t $=2\mathrm{.}0$ s$?$