1. The problem statement, all variables and given/known data Rocket motors make a rocket of mass of 2200kg accelerate at 2.5m/s^2 over a distance of 650m in deep space. What is the work done? 3. The attempt at a solution F=m*a 2200kg*2.5m/s^2 = 5500N 5500*650= 3575000 When I look at the answer page it tells me the force causing acceleration is 11000N. I generally cant see where this figure has come from. The only thing I can see if i double the answer I get it = the answer that is given wd= 7150000. The only other possible solution I can come to is that, the mass of the rocket decrease as it accelerates, so the original mass of rocket was 4400kg. If I used this figure it would give me the right answer. Is this the right train of thought?