A proton with a charge $\backslash (+$e $\backslash )$ is moving with a velocity $\backslash ($ v $\backslash )$ at $\backslash (40^\{\backslash$circ$\}\backslash )$ to the direction of a magnetic field $\backslash ($ B $\backslash ).$ The component of the resulting force on the proton in the direction perpendicular to $\backslash ($ v $\backslash )$ is