1. UNIT 2: TRANSPORTATION LESSON 2: NEWTON’S LAWS AND FLYING

2. By the end of this lesson you should be able to:  describe the scientific laws and principles that make flight possible Vocabulary & People of Interest  Newton’s First, Second and Third Laws  Inertia  Lift  Drag  Bernoulli’s Principle  Sir Isaac Newton LEARNING OUTCOMES

3.  Have you ever wondered how an airplane full of passengers, luggage, and millions of parts can climb high into the air and travel there for hours on end?  The ability of an airplane to fly can be explained by several scientific laws and principles. In this lesson you will learn about these laws and principles, and how they determine how a plane needs to be designed in order to fly through the air. NEWTON’S LAWS OF MOTION

4.  In the mid-1600s, Sir Isaac Newton discovered three laws that describe the motion of physical objects - including airplanes. NEWTON’S LAWS OF MOTION

5.  Newton's first law states that an object will remain at rest or in uniform motion unless it is compelled to change its state by an external force.  This is sometimes called the LAW OF INTERTIA. NEWTON’S FIRST LAW OF MOTION

6.  An airplane is actually acted upon by two sets of external and competing forces.  If a force in either set becomes more powerful than the other, it will change the state of the airplane, i.e., cause it to move from rest, speed up, slow down, change direction, or change altitude.  The two sets of forces acting on an airplane are: NEWTON’S FIRST LAW OF MOTION

7.  Lift: the force that pushes an airplane upwards  Weight: the downward force (gravity) that opposes lift  Thrust: the force that moves an airplane forward  Drag: the force (friction) that resists the airplane as it moves forward NEWTON’S FIRST LAW OF MOTION

8.  Newton's second law states that the greater the mass of an object, the more force is required to increase its speed.  The important point here for flight is that generating more force will increase the speed of an airplane. And what is the main part of the airplane that generates force?  That's right - the engine! The more powerful the engine or the harder it is asked to work, the more force it will create, and consequently the more speed it will generate. NEWTON’S SECOND LAW OF MOTION

9.  How that additional force creates more speed can be explained by Newton's third law. NEWTON’S SECOND LAW OF MOTION

10.  Newton's third law states that for every action there is an equal and opposite reaction.  In other words, if Object A applies a force on Object B, Object B applies an equal and opposite force on Object A. NEWTON’S THIRD LAW OF MOTION

11.  Newton's third law of action and reaction is very important for airplanes.  Think of the jet engine again: the engine exhausts hot gases and tremendous air pressure out the back (action), which in turn creates a thrusting forward in the opposite direction (reaction). NEWTON’S THIRD LAW OF MOTION

12.  Newton's third law thus helps to explain how an airplane is propelled forward on the ground and in the air. And the more force the engine creates, the more force pushes back against the airplane. This means more speed forward. NEWTON’S THIRD LAW OF MOTION

13.  Match the Reaction with the Force balances described: ACTIVITY a)Thrust equals drag_____The airplane takes off or climbs higher in the air b)Weight exceeds lift_____The airplane stays at the same altitude (in the air or on the ground) c)Thrust exceeds drag_____The airplane descends d)Lift exceeds weight_____The airplane moves forward e)Drag exceeds thrust_____The airplane stays at rest or maintains its current speed f)Lift equals weight_____The airplane slows down or stops

14.  Match the Reaction with the Force balances described: ACTIVITY a)Thrust equals drag__d__The airplane takes off or climbs higher in the air b)Weight exceeds lift__f__The airplane stays at the same altitude (in the air or on the ground) c)Thrust exceeds drag__b__The airplane descends d)Lift exceeds weight__c__The airplane moves forward e)Drag exceeds thrust__a__The airplane stays at rest or maintains its current speed f)Lift equals weight__e__The airplane slows down or stops

15.  So far we've talked about scientific laws and how they affect the flight of an airplane. These laws cannot be changed. Air travel is impossible unless the plane is designed to accept and take advantage of these laws. BERNOULLI’S PRINCIPLE

16.  Airplanes are also designed based on several widely accepted scientific principles.  One of the most important of these is Bernoulli's Principle.  Bernoulli's Principle states that the faster a fluid (such as air) travels, the less pressure it exerts. This explains how air travelling over and under the wing causes the airplane to lift off the ground and fly in the air. BERNOULLI’S PRINCIPLE

17.  This illustration shows a cross section of a typical airplane wing.  Notice how the top of the wing is curved and the bottom is basically flat.  When the airplane travels forward, air is deflected at the front edge of the wing.  Air going over the top travels a greater distance than the air going below.  As a result, it has to go faster to catch up at the back of the wing.  According to Bernoulli's Principle, slower air exerts more pressure than faster air.  This means the pressure exerted upwards on the wing from below is greater than the pressure exerted downwards on the wing from above. This pushes the plane upwards.  As you learned earlier in this lesson, this force is called lift.

18.  Can you see how Bernoulli's Principle is connected to Newton's laws of motion?  Remember that Newton said that an object remains at rest or in uniform motion unless an outside force makes it do something different.  Bernoulli's Principle describes how the shape of the airplane's wing can cause an outside force (lift) to make an airplane climb into the air.  The movement of air over and under the wing upsets the balance of lift and drag and forces the plane to change its current state. BERNOULLI’S PRINCIPLE

19. QUICK CHECK QUESTIONS