Answer
The final speed of the rocket sled is $~~190~m/s$
Work Step by Step
We can use conservation of momentum to find the final speed of the rocket sled:
$p_f = p_i$
$(2900~kg+920~kg)~v_f = (2900~kg)(250~m/s)$
$v_f = \frac{(2900~kg)(250~m/s)}{(2900~kg+920~kg)}$
$v_f = 190~m/s$
The final speed of the rocket sled is $~~190~m/s$.
