Forces, Planes and propellers

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Forces, Planes and propellers
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Topic 1 Forces

• A force is any influence that can change the
  trajectory, speed or shape of a body.
• Effects produced by a force
• Change in state of motion of a body
• Distortion of a body

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Forces

• Forces (measured in Newtons) are qualified by
  both direction and magnitude (represented by a
  vector)

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Forces
Magnitude
20N
Direction
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Forces

• Forces can
• Accelerate an object
• Force is applied in the same direction of the
  motion
• Decelerate an object
• Force is applied in the opposite direction of the
  motion
• Modify the trajectory
• Force is applied on the side of the object

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Forces

• What will be the total force?
• Resultant Force

30N
10N
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Forces

• What will be the resultant force?
• Resultant Force

30N
10N
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So lets say

• 2 people are each trying to push an elephant with
  a force of 40 N
• What is the resultant force?
• Equilibrium of forces

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Forces

• Resultant Force
• Forces in the same direction are added
• Forces in the opposite direction are subtracted
• Equilibrium of forces is achieved then the
  resultant force on an object is zero.
• When the forces acting on the object are of same
  magnitude and in opposing direction

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Forces

• Force (N) is any influence that can change the
  trajectory, speed or shape of a body.
• Change in state of motion of a body
• Distortion of a body
• A force is represented by a vector with both
  direction and magnitude

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Forces

• If a force is applied
• in the same direction as the motion of a body it
  will accelerate
• in the opposite direction as the motion of a body
  it will decelerate
• Perpendicularly to the direction of motion of a
  body it will change trajectories

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Forces

• An equilibrium of forces is achieved when the
  resulting force is equal to 0
• Add forces in the same direction
• Subtract forces in opposing direction

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Types of forces

• Magnetic Force
• Force of attraction/repulsion between two
  magnetic substances
• The FORCE

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Types of Forces

• Electromagnetic Force
• Force of attraction/repulsion between two charged
  objects
• Friction
• Force that resists relative motion between two
  bodies in contact.
• Depends on surface and pressure applied

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Types of Forces

• Gravitational Force
• Always towards the center of the Earth
• w Fg m g
• Where w weight (N)
• Fg Gravitational Force (N)
• g Gravitational Constant (N/kg)
• m Mass (Kg)

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Calculating gravitational force

• What is the mass of a 70 kg astronaut on Earth?
  (g 9.8)
• What is the mass of the same astronaut on the
  moon? (g1.67)
• What is the weight of the same astronaut on the
  moon? (g1.67)

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Types of forces

• Magnetic Force
• Force of attraction/repulsion between two
  magnetic substances
• Electromagnetic Force
• Force of attraction/repulsion between two charged
  objects

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Types of Forces

• Gravitational Force
• Always towards the center of the Earth
• w Fg m g
• Where w weight (N)
• Fg Gravitational Force (N)
• g Gravitational Constant (N/kg)
• m mass (kg)

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Application of forces

• The challenge of flight

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Forces of flight

• Drag
• force that opposes an aircraft's motion through
  the air
• Lift
• Force that directly opposes the weight of a plane
  (requires a fluid medium and motion)
• Gravity
• Thrust
• Force that moves an airplane forward

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Which forces should be larger?
                                                       
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How do we achieve this?
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Principle behind the propeller and wings

• Bernoullis Principle
• Shows the relation between velocity, pressure and
  density of a fluid
• An increase in speed of the fluid results in a
  decrease of pressure.

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Airplane wing application
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Airplane Propeller application
Low
Thrust
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Airplane Propeller application
Low
Thrust
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Propeller lingo

• Propeller Pitch
• The distance the propeller will travel through
  the fluid in one rotation
• Propeller angle
• The angle between the blade and the plane of
  rotation
• http//www.youtube.com/watch?vR7hyrD9-R4A

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• Torque Effect

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• Leading edge
• Edge of the blade that cuts through the wind
• Trailling edge
• Edge of the blade that does not cut through the
  wind

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• Twisting of the blades
• Due to the variation in the speed of rotation of
  the propeller (center vs. tip) a twist is given
  to meet the wind
• Makes sure that your propeller blades do not
  break apart in flight

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Bernoullis Principle

• An increase in speed of the fluid results in a
  decrease of pressure.

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