FAA Powerplant Written Practice Test

According to Newton's third law of motion, what occurs for every action?

1. There is a cause and effect

2. There is an equal and opposite reaction

3. Energy is conserved

4. Momentum is lost

The correct answer is: There is an equal and opposite reaction

Newton's third law of motion states that for every action, there is an equal and opposite reaction. This principle explains how forces work in pairs: whenever one body exerts a force on another, the second body exerts a force of equal magnitude but in the opposite direction on the first body. This behavior is fundamental to understanding how propulsion works in aviation and other areas of physics. For example, in a jet engine, as the engine expels exhaust gases backward, the aircraft is propelled forward with a force equal to the force of the exhaust gases being expelled. This demonstrates the practical application of the law in the realm of aerodynamics and flight mechanics. Understanding this concept is crucial for analyzing and predicting the behavior of aircraft and other objects in motion.