The design of a lunar mission calls for a 1200 -kg spacecraft to lift off from the surface of the moon and travel in a straight line from point $A$ and pass point $B$. If the spacecraft motor has a constant thrust of $2500 \mathrm{N}$, determine the speed of the spacecraft as it passes point $B .$ Use Table $\mathrm{D} / 2$ and the gravitational law from Chapter 1 as needed.