Step-by-step explanation:
It is given that,
Speed of the proton,

Electric field,

(a) Distance covered, d = 4 cm = 0.04 m
Let t is the time interval required for the proton to travel 4.00 cm horizontally. It can be calculated as :



or
t = 111 ns
(b) Since, initial speed = 0 in vertical direction. So,
So, q E = ma

Displacement is given by :




(c) For vertical component of velocity, use equation of kinematics as :
(d = 4 cm)



For horizontal component of velocity,



Hence, this is the required solution.