Final answer:
Placing the engine start switch to 'stop' in-flight for engines #2 or #3 would lead to the propellers feathering, reducing drag and maintaining lift without the engine's thrust. This process slows down and eventually stops the propeller blades from spinning, and is normally a part of emergency procedures.
Step-by-step explanation:
Placing the engine start switch to stop in flight for engine #2 or #3 would cause the propellers to feather. Feathering the propellers means they are adjusted to an angle that minimizes the drag on the engine, effectively stopping the blades from spinning. This is a safety measure typically used when an engine fails, allowing the aircraft to reduce drag and maintain lift as much as possible without the thrust from the inoperative engine. However, intentionally shutting down an engine in flight without an emergency is against standard operating procedures and could be hazardous.
Unreasonable Results
In the case where a propeller has been spinning at 10 revolutions per second and the engine is shut off, leading to a constant deceleration of 2.0 rad/s² over 40 seconds, the calculations for the rotation rate after this time can be performed. However, it's essential to consider if this scenario is realistic from an engineering standpoint; the change in propeller speed due to engine shutdown and the resulting deceleration might vary depending on several factors like aerodynamic forces and the propeller's inertia.