航空专业英语 Flight Theory 升力的产生.pptx

3.2The Creation of Lift ;3.2 The Creation of Lift（升力的产生）;Two basic laws of physics,Newton’s Third Law of Motion and Bernoulli’s Principle,help explain the phenomennon of flight.;Newton’s first law?states, in part, that: A body at rest tends to remain at rest, and a body in motion tends to remain moving at the same speed and in the same direction.;Newton’s second law?implies that: When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force.;Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction.;If you could observe the airflow in front of and behind an airplane in flight,you would see that the air behind the airplane is redirectedly downward.;The downward force caused by the wing is called downwash.;The action of redirecting the air down causes the reaction of lifting the airplane.;Only when the mass of air directed down by the wings equal the mass of the airplane does the airplane fly.