Answer:
the overall velocity of the second stage after separation is = 1240 m/s.
Step-by-step explanation:
We are told that the first stage is three times as massive as the second stage.
Now, If the second stage has mass M, the total mass of the first and second stages = M + 3M = 4M.
Now, since the stages are separating at 40 m/s, the lighter second stage must have received most of that velocity change which by proportion is; (3/4) x 40 = 30 m/s
Thus, stage two has added 30 m/s to its velocity.
Thus, the overall velocity of the second stage after separation is now;
1210 + 30 m/s = 1240 m/s.