In this case, there are three forces acting on the
car: the friction force powered by its engine, F,
the contact force from the car behind, F2/1, and
the drag force due to air resistance, Fd′, cancelling
out the other two forces. There is no drag force
on the second car and, since F2/1 = F, the total net force pushing the front car forward is now twice
as large as for the single car, so one can easily
anticipate the two-car system will move faster
than the single car in the previous situation.