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Aerodynamics Physics project 2011

concepts behind forces that interact with an elastic-powered aeroplane, as well as factors affecting its movement

caleb phee

on 6 July 2011

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Transcript of Aerodynamics Physics project 2011

3 2 Too much to the rear- Because of this the mass
near the rear of the plane increases. Thus the power
of the drag increases resulting in a very short flight.
This is also due to the fact that, the rear has relatively
more gravity acting on it and will be vertically be
pulled to the ground very quickly from the launch. Too much to the front- Because of this
the mass near the propeller of the plane increases.
Thus the power of the thrust of the propeller
decreases resulting in a very short flight. 1 3 possible wing
positions Physics behind a rubber-band airplane Center of gravity definition The imaginary point in a system of bodies or an
extended body at which the mass of
the system may be considered to be
concentrated At which external forces may be considered to be applied The right center of gravity- Because
the mass of the plane is well balanced at the front and back making it a good centre of gravity for a smooth flight deduction From this we might have deduced that the centre of gravity is
somewhat related to the wing's position. This is so because, the
propeller’s mass and the rear wing’s mass are balanced.
Thus the real difference in center of gravity depends on the wings' position. conclusion The wing should be a 1/4 of a plane from the propeller to have a nice flight. ENERGY Elastic Potential Energy Kinetic Energy The kinetic energy of an object is a
scalar amount of energy which it
possesses due to its motion
The work needed to accelerate
a body of a given mass from rest
to its stated velocity Definition formula KE = 0.5mv2
where m = mass and v = speed

This equation shows that the kinetic energy of an object is directly proportional to the square of its speed. That means that for a twofold increase in speed, the kinetic energy will increase by four. EPE vs KE Since in a rubber band plane, the kinetic energy is derived from the elastic potential energy, we were able to derive a trend between the two, which is, the larger the amount of elastic potential energy, the more kinetic energy the plane has. Potential energy exists when a force acts upon an object that tends to restore it to a lower energy configuration. This force is often called a restoring force. When does it exist? For example, when a rubber band is being twined up in a clockwise manner, there is a force in the opposite direction that is trying to revert it back to its untwined position and this opposite directional force is the restoring force of the rubber band. The initial force that is used to twine the rubber band is then stored in the rubber band. Why is energy stored? According to the law of conservation, since energy cannot be
created or destroyed, it is then stored as elastic potential energy,
which is converted into kinetic energy once the restoring force acts on it. Calculation of
elastic potential energy The formula of calculating elastic potential energy in a rubber band goes by the formula :
PEs = 0.5kx 2

Where 1. PEs is elastic potential energy,
2. k is the net displacement from the equilibrium
3. x is the equilibrium. Using this formula, it is possible to calculate
exactly how much elastic potential energy is
stored in the rubber band. Factors affecting EPE Thickness of the rubber band length of the rubber band the number of turns Results form a parabolic arc.
An extremely thick rubber band hampers the flight of the airplane because a thick rubber band is extremely heavy; making the plane unable to fly for a long time.
Besides, the extremely thick rubber band results in very high levels of Elastic Potential Energy stored in the rubber band, and this causes there to be a lot of friction between the propeller and the shaft.
We have reached a conclusion that there is an optimal thickness of a rubber band that is not to heavy and it does not have that much friction. This enables the propeller to spin for the longest time and also allows the plane to fly for the longest time. Data also forms a parabolic arc.
When the rubber band is 10cm, the rubber band is too tight at the beginning! This means that the tension after being wound up is very great, this results in a lot of friction between the propeller and the shaft.
However, as the length increases, the propeller spin time and flight time gradually increase as while there is sufficient Elastic Potential Energy to enable take off, there is less friction to be overcome.
When the string becomes too slack, you will notice an unusual trend. That the propeller spin time still increases yet the flight time drops drastically.
This is because the Elastic Potential Energy is spread out over an extremely long rubber band, this allows the propeller to spin for an extremely long time, yet the energy is insufficient to sustain flight.
We can conclude from our experiment that the rubber band must not be too short nor can it be too long. After doing more research online, it has been proven that a rubber band that is 1.5 times the length of the shaft of the plane is most optimal for sustaining flight. The outcome was very close to our hypothesis.
The more times the rubber band was turned, the longer the propeller spin time and the flight time.
With more turns, the amount of Elastic Potential Energy increases. When there is more Elastic potential energy, more stored energy that is converted into kinetic energy.
This obviously leads to longer flight time.
We further analysed this on the internet and we discovered a formula to calculate the maximum number of turns based on the length and the width of the rubber band. : Aerodynamics Lift -component of aerodynamic force perpendicular to the relative wind. Newton's 3rd law of motion Based on Newton’s 3rd law, every action will have an opposite reaction, as the wings move through the air at a slight angle of attack, a downward deflection of air will be forced. The opposite reaction to that is an upwards thrust of the air molecules under the wing, thus causing lift. Also, the larger the angle of attack, the more force is exerted on the underside of the wing. The higher the speed of the plane, the upward force also increases. (The air motion is seen by the red arrows below) Drag -component of aerodynamic force parallel to the relative wind
-opposite force of thrust types of drag Friction drag the aircraft travels through the air, air will resist the motion of the aircraft. Form Drag The shape of the plane will also affect the amount of drag. The more streamlined it is (elliptical), the less drag it will produce. However if it is shaped in a blunt manner and not streamlined, it will produce more drag. Induced Drag -drag which is actually the opposite reaction of lift For lift to be produced, the wing must approach the wind at an angle of attack, in order to deflect the wind to create lift. As the relative wind hits the wing, drag is produced. Weight -the force directed downward from the center of mass of the airplane towards the center of the earth. It is proportional to the mass of the airplane times the strength of the gravitational field. Thrust is simply the propulsion system of the plane. In this case, it consists of the propeller and the coiled rubber band. It should be placed parallel to the body for the plane to fly forward. Thrust -the force produced by the engine. It is directed forward along the axis of the engine. Weight is simply the opposite force of lift and is caused by gravity. In order to climb, the upward force (lift) must overcome the weight. As our rubber band plane will not achieve much upward force as it does not fly at a very high speed nor does it have the curved wing structure, it cannot be very heavy. This is important so that the lift is able to overcome the weight force for the plane to fly. Thank You, and have a nice day
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