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Flight. Kinetic Energy. Kinetic energy is energy of motion All moving objects have kinetic energy Different moving objects have different amounts of kinetic energy Amount of kinetic energy an object has depends on the mass and speed of the object. Potential energy.

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kinetic energy
Kinetic Energy
  • Kinetic energy is energy of motion
  • All moving objects have kinetic energy
  • Different moving objects have different amounts of kinetic energy
  • Amount of kinetic energy an object has depends on the mass and speed of the object
potential energy
Potential energy
  • Potential energy is energy that is stored, not being used
  • It is energy that comes from position or condition
  • More potential energy something has - more kinetic energy it will have when potential energy is transformed to kinetic energy
gravitational potential energy
Gravitational Potential energy
  • Gravitational potential energy – stored because of an object’s height, changes to motion (kinetic) energy
  • Gravitational potential energy is affected by position
  • 2 objects having the same mass at different heights, the higher object will have more potential energy
gravitational potential energy1
Gravitational Potential energy
  • Gravitational potential energy is affected by mass
  • 2 objects at the same height having different masses, the object with more mass will have more potential energy
gravitational potential energy transforming into kinetic energy
Gravitational Potential energy transforming into Kinetic energy
  • Higher above the ground, the more gravitational potential energy an object has, which can be transformed into kinetic energy
  • Faster an object falls, the more kinetic energy it has
  • Kinetic energy increases as an object speeds up when it falls and gravitational potential energy decreases
kinetic energy transforming into gravitational potential energy
Kinetic energy transforming into Gravitational Potential energy
  • A falling object arrives at the ground having no gravitational potential energy and lots of kinetic energy as it touches the ground
  • Transfer kinetic energy to potential gravitational energy by lifting or raising an object above the ground, kinetic energy decreases and gravitational potential energy increases
elephant and feather free fall
Elephant and feather – free fall
  • Force of gravity on two objects of different masses
  • http://www.physicsclassroom.com/mmedia/newtlaws/efff.cfm
  • In a vacuum, objects all fall to theground due to the force of gravity
  • Force of gravity causes all objectsto accelerate towards the groundat 9.8 m/s2
  • RememberF = m x a
free fall from 1 5 m
Free fall from 1.5 m
  • In a vacuum, an object should take 0.56 sec to fall 1.5 m
elephant and feather with air resistance drag force
Elephant and feather with air resistance (drag force)
  • Force of gravity on two objects of different masses with air resistance (drag force)
  • http://www.physicsclassroom.com/mmedia/newtlaws/efar.cfm
  • Objects in air encounter air molecules when they fall
  • Objects apply a force on the air molecules and the air moleculesapply a force on the falling object
drag force
Drag force
  • Drag force: the force exerted by the fluid (air or water) on the object moving through the fluidThe force is dependent on the motion of the object, the properties of the object, and the properties of the fluid that the object is moving through.
drag force1
Drag force
  • Drag force, acts opposite to the motion of the object
  • For a falling object, drag force counteracts the force of gravity
  • Drag force is created by air molecules colliding with a falling object
  • Drag force causes objects to fall more slowly than the same objects falling in a vacuum
factors that affect drag force
Factors that affect drag force
  • Two most common factors that have a direct effect upon the amount of drag force are:
  • cross-sectional area of the object (surface area) and speed of the object
  • Increased cross-sectional (surface) areas result in an increased amount of drag force.
  • Increased speeds result in an increased amount of drag force.
drag force and surface area
Drag force and surface area
  • Increased cross-sectional (surface) area results in an increased amount of drag force.
  • Increased surface area results in increased falling flight time
drag force and speed
Drag Force and speed
  • Drag force also depends upon the speed of the object. A falling object will continue to accelerate to higher speeds until it encounters an amount of drag force that is equal to its weight.
  • Objects that weigh more (experience a greater force of gravity), it will accelerate to higher speeds before reaching a terminal velocity.
terminal velocity
Terminal velocity
  • As an object falls, it picks up speed. The increase in speed leads to an increase in the amount of air resistance.
  • Eventually, the force of air resistance becomes large enough to balance the force of gravity.
  • At this instant in time, the net force is 0 Newton; the object will stop accelerating. The object is said to have reached a terminal velocity.
  • The change in velocity terminates as a result of the balance of forces. The velocity at which this happens is called the terminal velocity.
weight
Weight
  • Force of gravity on an object is also known as the weight of the object
  • Force of gravity (weight) = mass x acceleration due to gravity
  • Force of gravity (weight) = mass (kg) x 9.8 m/s2
  • Unit for weight is Newtons (N) because weight is a force, 1 N = 1 kg m/s2
mass and falling flight time
Mass and falling flight time
  • More massive objects weigh more (experience a greater force of gravity) than less massive objects.
  • More massive objects fall faster than less massive objects because they are acted upon by a larger force of gravity; for this reason, they accelerate to higher speeds until the air resistance force equals the gravity force.
mass and falling flight time1
Mass and falling flight time

If the surface areas of the objects are the same, then the drag force on the objects is the same. Because gravity exerts a greater force on the more massive parachuter, then the larger object will speed up faster toward the ground.

four forces on a plane or other flying object
Four forces on a plane or other flying object

Credit: National Air and Space Museum, Smithsonian Institution

slide21

When an airplane is flying straight and level at a constant speed, the lift it produces balances its weight, and the thrust it produces balances its drag.

  • However, this balance of forces changes as the airplane rises and descends, as it speeds up and slows down, and as it turns.
slide22
Drag

Credit: National Air and Space Museum, Smithsonian Institution

Drag is the force that acts opposite to the direction of motion. Drag is caused by air molecules colliding with an object and differences in air pressure.

slide23
Drag
  • Drag force, acts opposite to the motion of the object
  • For a falling object, drag force counteracts the force of gravity
  • For an object flying horizontally (parallel to the ground), the drag force acts horizontally
  • More surface area facing the direction of motion, the more drag force
weight force of gravity
Weight (force of gravity)

Credit: National Air and Space Museum, Smithsonian Institution

Weight is the force of gravity. It acts in a downward direction—toward the center of the Earth. Force of gravity (weight) = mass (kg) x 9.8 m/s2.

slide25
Lift

Credit: National Air and Space Museum, Smithsonian Institution

LIftis the force that acts at a right angle (perpendicular) to the direction of motion through the air. Lift is created by differences in air pressure (number of air molecules colliding with an object).

slide26
Lift
  • Lift force is affected by surface area and speed of the object
  • An object with horizontal speed has kinetic energy, the higher the object is, the more potential energy the object also has
  • An object that can’t create enough horizontal speed to generate lift force can fall from a height - converting potential energy to kinetic energy which can then be turned into motion to create lift force
slide27
Lift
  • Greater mass creates a greater force of gravity and requires a larger lift force to take off
  • Greater mass requires a faster speed to increase lift force
  • Greater surface area leads to a larger lift force - a slower speed is needed to create enough lift force to overcome force of gravity and take off
  • Smaller surface area needs more speed to take off than a larger surface area
changing wing orientation changes forces
Changing wing orientation changes forces
  • Horizontal wing, falling object – motion down, large surface area has large drag force, slower speed of falling
  • Vertical wing, falling object – motion down, small surface area, small drag force, faster speed of falling
thrust
Thrust

Credit: National Air and Space Museum, Smithsonian Institution

Thrustis the force that propels a flying object in the direction of motion. Engines or flapping wings produce thrust.

thrust1
Thrust
  • Wings push down and back against the air
  • Air pushes back against the wings with an equal and opposite force (Newton’s Third Law of Motion)
  • Thrust motion on the object causes it to speed up in a forward and upward direction
  • Greater forward speed increases lift force and helps object remain in the air
potential energy to kinetic energy birds
Potential energy to kinetic energy, birds
  • Birds with wings use pectoral (chest) muscles to produce flapping motion
  • Chemical potential energy in food is converted in muscle cell mitochondria into energy that becomes kinetic energy of flapping wings
wing surface area and mass
Wing surface area and mass
  • Birds with small wing surface area relative to body mass must flap wings frequently to sustain flight
  • Birds with large wing surface area relative to body mass can flap less and glide more to sustain flight
  • Wing loading – ratio of mass to wing area
  • Activities related to wing loading, comparing birds and planes (website in general has good info on flight) http://www.sciencelearn.org.nz/Contexts/Flight/Science-Ideas-and-Concepts/Wing-loading
potential energy to kinetic energy ornithopter
Potential energy to kinetic energy, ornithopter
  • Ornithopter stores energy (potential strain energy) in the twists of an elastic band
  • Untwisting the band converts to kinetic energy of flapping wings
  • Flapping wings push down and back on the air which applies an up and forward thrust force on the bird
  • Thrust force keeps the bird in the air longer than gliding alone, more potential energy gives more kinetic energy and longer flight time
flapping bird wings
Flapping bird wings
  • Motion of flapping bird wings pushes backwards against the air, the air pushes forward on the bird increasing thrust force and bird’s forward speed
  • Increasing thrust force and forward speed also increases the lift force on the bird helping to keep it in the air
  • Motion of flapping bird wings pushes down against the air, the air pushes upward on the bird keeping bird in the air