Felectric = q*E
Ftranslational = m*a
Felectric = Ftranslational
q*E = m*a
Solve for a
a = q/m*E
Our sign convention is "up is positive"
q = 1.6*10^-19 C
m = 1.67*10^-27 kg
E = -150 N/C (- because it is down and up is positive)
a =
-6,4*10^5 m/s^2 (downward)
answer
a = -6,4*10^5 m/s^2 (downward)