The air exerts a forward force of 10 N on the propeller of a .20-kg model airplane. If the plane accelerates forward at 2.0 m/s^2, what is the magnitude of the resistive force exerted by the air on the airplane?

1 Answer
Nov 24, 2015

9.6N

Explanation:

Using newtons second law
Fnet=ma
What is the net force of the plane? It is primarily forward but encounters some air resistance. So first, draw your free body diagram.
http://www.funpaperairplanes.com/learn_about_flight.htmlhttp://www.funpaperairplanes.com/learn_about_flight.html

In our case, the magnitude of the thrust force is greater than the drag, so our Net force would be Thrust - Drag.

Note* For convenience, I will use Fd as drag force and P as thrust force.
Fnet=ma
P-Fd=ma
10-Fd=(0.20kg)(2.0m/s^2)
10-Fd=0.4N
-Fd=-9.6
Fd=9.6N