posted by savy .
The air exerts a forward force of 10 N on the propeller of a 0.20 kg model airplane. If the plane accelerates forward at 5.0 m/s2, what is the magnitude of the resistive force exerted by the air on the airplane in Newtons ?
Fnet = Fprop - Friction = m*a
Solve for the resistive force, which I have called Ffriction
Fprop is the forward thrust of the propeller.
You know what m and a are.