In the cathode-ray tube, electrons having a mass m
are emitted from a source point S and begin to travel
horizontally with an initial velocity v₀. While passing
between the grid plates a distance l, they are subjected to a
vertical force having a magnitude eV/w, where e is the
charge of an electron, V the applied voltage acting across
the plates, and w the distance between the plates. After
passing clear of the plates, the electrons then travel in
straight lines and strike the screen at A. Determine the
deflection d of the electrons in terms of the dimensions of
the voltage plate and tube. Neglect gravity which causes a
slight vertical deflection when the electron travels from S to
the screen, and the slight deflection between the plates.

See attachment for picture

2. Relevant equations

∑F_y = ma_y

v_y = a_yt

3. The attempt at a solution

eV/w = ma_y
Hence, a_y = eV/mw

By kinematics, from the start to the end of the plates (length l)

v_y= v0 + a_yt

How do I get the time for this interval? (between the plates)