Serway & Jewett — Conservation of Energy: Problem 39

An airplane of mass \(1.50 \times 10^4 \text{ kg}\) is in level flight, initially moving at \(60.0 \text{ m/s}\). The resistive force exerted by air on the airplane has a magnitude of \(4.0 \times 10^4 \text{ N}\). By Newton’s third law, if the engines exert a force on the exhaust gases to expel them out of the back of the engine, the exhaust gases exert a force on the engines in the direction of the airplane’s travel. This force is called thrust, and the value of the thrust in this situation is \(7.50 \times 10^4 \text{ N}\). (a) Is the work done by the exhaust gases on the airplane during some time interval equal to the change in the airplane’s kinetic energy? Explain. (b) Find the speed of the airplane after it has traveled \(5.0 \times 10^2 \text{ m}\).