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have you ever looked up at the sky and
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wondered how massive airplanes weighing
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tons manage to lift off and stay
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airborne the answer lies in the
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fascinating world of aerodynamics and
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the laws of physics in this video we'll
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break it all down in a simple and
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engaging way so strap in and let's take
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off the law of conservation of energy
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states that energy cannot be created or
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destroyed only transformed from one form
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to another motion is defined as the
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process of changing position relative to
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a reference point an object may appear
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to be in motion relative to one frame of
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reference while stationary relative to
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another for example a passenger seated
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inside an aircraft traveling at 200
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knots is motionless with respect to the
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aircraft but is moving at the same speed
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as the aircraft relative to the
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surrounding air and the earth air has no
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force or power except pressure unless it
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is in motion when it is moving however
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its Force becomes apparent a moving
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object in Motionless air has a force
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exerted on it as a result of its own
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motion it makes no difference in the
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effect then whether an object is moving
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with respect to the air or the air is
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moving with respect to the object the
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flow of air around an object caused by
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the movement of either the air or the
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object or both is called the relative
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wind the term ter speed and velocity are
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often used interchangeably but they do
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not have the same meaning speed is the
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rate of motion in relation to time and
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velocity is the rate of motion in a
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particular direction in relation to time
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for example an aircraft starts from New
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York City and flies 10 hours at an
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average speed of 260 mph at the end of
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this time the aircraft may be over the
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Atlantic Ocean Pacific Ocean Gulf of
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Mexico or if it's flight were in a
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circular path it may even be back over
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New York City if this same aircraft flew
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at a velocity of 260 m per hour in a
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southwestward direction it would arrive
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in Los Angeles in about 10 hours only
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the rate of motion is indicated in the
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first example and denotes the speed of
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the aircraft in the last example the
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particular direction is included with
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the rate of motion thus denoting the
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velocity of the aircraft acceleration is
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defined as the rate of change change of
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velocity an aircraft increasing in
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velocity is an example of positive
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acceleration while another aircraft
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reducing its velocity is an example of
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negative acceleration or deceleration
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the fundamental laws governing the
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action of air about a wing are known as
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Motion Newton's first law is normally
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referred to as the law of inertia it
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simply means that a body at rest does
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not move unless force is applied to it
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if a body is moving at uniform speed in
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a straight line Force must be applied to
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increase or decrease the speed according
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to Newton's law since air has mass it is
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a body when an aircraft is on the ground
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with its engines off inertia keeps the
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aircraft at rest an aircraft is moved
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from its state of Rest by the thrust
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Force created by a propeller or by the
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expanding exhaust or both when an
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aircraft is flying at uniform speed in a
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straight line inertia tends to keep the
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aircraft moving some external force is
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required to change the aircraft from its
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path of flight Newton's second law
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states that if a body moving with
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uniform speed is acted upon by an
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external Force the change of motion is
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proportional to the amount of the force
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and motion takes place in the direction
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acts for example an aircraft flying into
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a headwind will experience a reduction
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in ground speed due to the opposing
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Force similarly a crosswind will push
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the aircraft off course and let
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corrective control inputs are made
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Newton's third law is the law of action
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and reaction this law states that for
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everyaction there is an equal and
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opposite reaction this law can be
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illustrated by the example of firing a
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gun the action is the forward movement
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of the bullet while the reaction is the
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backward recoil of the gun these three
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laws collectively govern all aspects of
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flight and are continuously at play in
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aircraft motion Boli's principle states
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that when a fluid flowing through a tube
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reaches a constriction or narrowing of
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the tube the speed of the fluid flowing
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through that constriction is increased
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and its pressure is decreased the
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cambered surface of an air foil affects
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the air flow exactly as a constriction
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in a tube affects air flow as the air
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flows over the upper surface of an air
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foil its velocity increases and its
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pressure decreases an area of low
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pressure is formed there is an area of
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Greater pressure on the lower surface of
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the air foil and this great pressure
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tends to move the wing upward the
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difference in pressure between the upper
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and lower surfaces of the wing is called
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lift 34s of the total lift of an air
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foil is the result of the decrease in
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pressure over the upper surface the
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impact of air on the under surface of an
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air foil produces the other 1/4 of the
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lift these principles form the
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foundation of aerodynamic Theory and are
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crucial to understanding flight
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mechanics thanks for watching
