Answer
Vertical distance travelled =$0.26\times10^{-12}m$.
The designers need not worry about the gravitational effect, because the distance travelled is negligible.
Work Step by Step
Horizontal velocity is constant, so $t=\frac{S}{v}=\frac{0.35m}{1.5\times10^{6}m/s}=0.23\times10^{-6} s$
In this time, vertical distance travelled$=ut+\frac{1}{2}at^{2}=0+0.5\times9.8\times(0.23\times10^{-6})^{2}=0.26\times10^{-12}m$
The designers need not worry, because the distance travelled is negligible.
