I've never seen it in a HSC paper but I have seen questions before. They're quite difficult and my school never went through them so I wouldn't count on it being in an exam.
It's quite common for them to ask for the theory about that though so make sure you have it covered .
You could be as the formula for momentum is given on the formula sheet and the prelim course is assumed knowledge, I wouldnt be surprise if a trial paper asked this but unlikely in the hsc
But I think this dot point is more about how the law of conservation of momentum allows a rocket to be propelled, so more about applying the theory to the situation rather than calculations.