Answer
$v=60m/s$
Work Step by Step
We can determine the required speed as follows:
We apply the principle of impulse and momentum in the $y$-direction:
$mv_{y_1}+\Sigma \int_{t_1}^{t_2}F_ydt=mv_{y_2}$
We plug in the known values to obtain:
$2(-90)+\frac{1}{2}(0.4\times 10^{-3})(500\times 10^3)=2v$
This simplifies to:
$v=60m/s$
