U5 Flight

U5 Flight

1. Gravity

   • The pull towards the centre of Earth that we experience all the time.
     • Acceleration due to gravity (symbol g) of every object of g = 9.8 m/s2
       • F = m a or W = m g

2. Density is the mass to volume ratio.

   • Density is the same in a uniform fluid, even if the mass above the object changes when it si lower or higher in the fluid.
   • p = m/V (Unit: kg/m3)
   • Flying crafts that are heavier than air are called aerodynes.
     • Their average density is heavier than the density of air.

3. Pressure

   • Pressure is the concentration of a force over the surface area of an object.
     • Pressure (P) = Force (F) / Surface area (A)
       • Units: N/m2
   • Pressure in fluid increases with depth.
     • pressure (P) = density (p) * gravity (g) * depth (m)
     • Archimedes' principle
       • The size of the buoyancy force (symbol B: unit N): B = pgV (V is volume, unit m3)
         • New formula to calculate the object's weight: W = pgV or mg = pgV

4. Buoyancy

   • Air and water are both fluids.
     • Fluids exert an upwards buoyancy force on objects that are immersed in them.
     • Dynamic lift is a force caused by an object moving through a fluid.
     • When a fluid is air, the force is called aerodynamic lift.
       • Hot air balloons and airships are called aerostats
         • Lighter than air is the weight of the air that they displace is greater than the weight of the craft
           • Airships: The Hindenburg disaster.

5. Fixed-wing aircraft

   • A powered fixed-wing aircraft is an aeroplane.
     • Propulsion with a propeller, see Bernouilli's principle
   • An unpowered fixed-wing aircraft is a glider
     • Pilot must find places of rising air or thermals.
   • Bernouilli's principle
     • The pressure below the aerofoil is greater than the pressure above the wing.
       • The presure in a moving fluid is at right angles to the direction of motion on the fluid.
         • If the speed of a fluid is high, the pressure is low.
         • If the speed of a fluid is low, the pressure is high
   • Impact of travel on climate change.
   • Rockets
     • If the rocket can force gas to move backwards, the gas will force the rocket to move forwards.
       • Rockets do not need the atmosphere, like propellers to operate.

6. Momentum (p, Kg m/s)

   • P = m v (m is mass (kg); v is velocity (m/s)
     • Law of conservation of linear momentum
       • The total, combined linear momentum of both objects before and after the interaction is the same.

7. Rotor aircraft

   • A rotor at the front of an aeroplane is desined so that , when spinning thep ressure in front of the rotor is lower than the pressure behind the rotor.
     • This provides the thrust to move the aircraft along.
   • Helicopter