An airplane of mass 1.50 x 104 kg is moving at 60.0 m/s. The pilot then increases the engine’s thrust to 7.50 x 104 N. The resistive force exerted by air on the airplane has a magnitude of 4.00 x 104 N. (a) Is the work done by the engine on the airplane equal to the change in the airplane’s kinetic energy after it travels through some distance through the air? Is mechanical energy conserved? Explain. (b) Find the speed of the airplane after it has travelled 5.00 x 102 m. Assume the airplane is in level flight throughout the motion.