Question

Car A weighing 4000 lb and car B weighing 3700 lb are at rest on
a 22-ton flatcar which is also at rest. Cars A and B then accelerate
and quickly reach constant speeds relative to the flatcar of 7 ft/s
and 3.5 ft/s, respectively, before decelerating to a stop at the opposite
end of the flatcar. Neglecting friction and rolling resistance,
determine the velocity of the flatcar when the cars are moving at
constant speeds.

Answer 1