Answer
The speed of the flatcar is $~~0.54~m/s$
Work Step by Step
We can use conservation of momentum to find the speed of the flatcar:
$p_f = p_i$
$(242~kg+2140~kg)~v_f = (242~kg)(5.3~m/s)$
$v_f = \frac{(242~kg)(5.3~m/s)}{(242~kg+2140~kg)}$
$v_f = 0.54~m/s$
The speed of the flatcar is $~~0.54~m/s$.
