A rocket moving at 2000 m/s with a mass of 2000 kg releases gas at 500 m/s perpendicular to the direction of the rocket. The rocket moves at 18 degrees opposite of the direction that the gas was released. What is the mass of the gas released?

1 answer

There is no change of momentum of anything in the original, call it x, direction. Both the rocket and the expelled gas will continue to move at 2000 m/s

In the y direction. the gas moves in the + y direction and the rocket moves in the - y direction. However the total y momentum of the system remains zero since there was no net force on the system.
If the mass of gas is m, the remaining mass of the rocket is (2000-m)
the y direction speed of the remaining rocket is -2000 tan (18) = -650 m/s
The y momentum of the gas is m (+500)
The y momentum of the remaining rocket is (2000-m)(-650)
so
500 m -650(2000-m) = 0