User:Rolo Tamasi/Sandbox

Briefly stated, the three laws are:

An object in motion will remain in motion unless acted upon by a net force.
Force equals mass multiplied by acceleration.
To every action there is an equal and opposite reaction.

The statements of the laws

Newton's laws of motion describe the acceleration of massive objects. The modern understanding of Newton's three laws of motion is:

First Law: If no net force acts on a particle, then it is possible to select a set of reference frames, called inertial reference frames, observed from which the particle moves without any change in velocity.
Second Law: Observed from an inertial reference frame, the net force on a particle is proportional to the time rate of change of its linear momentum: $F=d[mv]/dt$ . Momentum is the product of mass and velocity. This law is often stated as $F=ma$ (the force on an object is equal to its mass multiplied by its acceleration).
Third Law: Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line.

In the given interpretation mass, acceleration and most importantly force are assumed to be externally defined quantities. This is the most common, but not the only interpretation: one can consider the laws to be a definition of these quantities. Notice that the second law only holds when the observation is made from an inertial reference frame, and since an inertial reference frame is defined by the first law, asking a proof of the first law from the second law is a logical fallacy.

Newton's first law: law of inertia

The statements of the laws Newton's laws of motion describe the acceleration of massive objects. The modern understanding of Newton's three laws of motion is:

First Law If no net force acts on a particle, then it is possible to select a set of reference frames, called inertial reference frames, observed from which the particle moves without any change in velocity. Second Law Observed from an inertial reference frame, the net force on a particle is proportional to the time rate of change of its linear momentum: F = d[mv] / dt. Momentum is the product of mass and velocity. This law is often stated as F = ma (the force on an object is equal to its mass multiplied by its acceleration). Third Law Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. The strong form of the law further postulates that these two forces act along the same line. In the given interpretation mass, acceleration and most importantly force are assumed to be externally defined quantities. This is the most common, but not the only interpretation: one can consider the laws to be a definition of these quantities. Notice that the second law only holds when the observation is made from an inertial reference frame, and since an inertial reference frame is defined by the first law, asking a proof of the first law from the second law is a logical fallacy.

Newton's first law: law of inertia

+ There is a major flaw in the downwash/momentum theory of lift. Whilst downwash and downward momentum may be produced as a consequence of lift (through induced drag for instance), it is however not the cause of lift. In two dimensional airfoil theory (potential flow), there is no net momentum produced in the fluid by the airfoil. Anecdotally, there can be no net flow of fluid in any direction because fluid cannot accumulate anywhere. The flow that goes down, must circulate upward somewhere else, hence zero net momentum. Since there is no net momentum produced in the fluid by the action of the airfoil, there can be no lift generated by this mechanism. There must be another explanation of lift other than the "downward momentum or deflection-reaction theory". I am apparently not permitted to publish the "Curvature Theory of Lift" in this forum because it is classed as Original Work by Wikipedia. It is a faily simple theory and only takes ten lines of simple mathematics to prove. The result however is the same as produced by the Bernoulli Equation.Markosvincios 05:53, 20 October 2007 (UTC)

In order for a wing to produce lift it has to be at a positive angle to the airflow. In that case a low pressure region is generated on the upper surface of the wing which draws the air above the wing downwards towards what would otherwise be a void after the wing had passed. On the underside of the wing a high pressure region forms accelerating the air there downwards out of the path of the oncoming wing. The pressure difference between these two regions produces a net upwards force on the wing, called lift.

The pressure differences, the acceleration of the air and the lift on the wing are intrinsically one mechanism. It is therefore possible to derive the value of one by calculating another. For example lift can be calculated by reference to the pressure differences or by calculating the energy used to accelerate the air. Both approaches will result in the same answer if done correctly. Debates over which mathematical approach is the more convenient can be wrongly perceived as differences of opinion about the principles of flight and often create unnecessary confusion in the mind of the layman.

For a more detailed coverage see lift (force).

A common misconception is that it is the shape of the wing that generates lift by having a longer path on the top rather than the underside. This is not the case, thin flat wings can produce lift efficiently and aircraft with cambered wings can fly inverted.

The common aerofoil shape of wings is due to a large number of factors many of them not at all related to aerodynamic issues, for example wings need strength and thus need to be thick enough to contain structural members. They also need room to contain items such as fuel, control mechanisms and retracted undercarriage. The primary aerodynamic input to the wing’s cross sectional shape is the need to keep the air flowing smoothly over the entire surface for the most efficient operation. In particular, there is a requirement to prevent the low-pressure gradient that accelerates the air across the top of the wing becoming too great and effectively “sucking” the air off the surface of the wing. If this happens the wing surface from that point backwards becomes substantially ineffective.

http://en.wikipedia.org/wiki/Wing#Science_of_wings

Wing#Science_of_wings

I am a recent visitor to these pages and, having read everything here, including discussions overflowing into other talk pages and having browsed the history I would like to tell a story. I hope it will be received constructively as it is intended.

Albert had owned his car for many years, he maintains it himself and, at least once a week he washes and polishes it by hand. He knows every inch of the car, it is very old and simple. He loves it so much he has joined a club with members all over the world with identical cars, which they all love and understand with a passion, he has even given his car a name.

One Sunday afternoon Albert is lying in the sun relaxing after giving his car its weekly polish when Bill walks past. Bill has had many cars and has even participated in some motor sports but he is not an expert like Albert. The previous evening he had seen Albert driving past and had noticed how brilliant and white the headlamps were when compared to his own.

Bill asks Albert how his lights are so bright and white. “Its easy” says Albert “I have fitted Xenon bulbs”. Bill sighs, he knew it would be complicated; he doesn’t even know what Xenon is, he wished he were an expert like Albert. “You can do it too, just buy them from the shop and pop them in.” reassures Albert.

Neither of them had seen Charlie approaching from the completely opposite direction. “That wont work, the lights are clearly red, you cant used Xenon bulbs.”

“Not again.” groans Albert closing his eyes and going back to his daydream.

“But I can see they are white” responds Bill.

“No they are red, look I have a light gauge here and you can see the colour temperature is several thousand kelvin away from what is considered white.”

“I’m sorry, I don’t understand your explanation and I can see they are white.”

“Well that is impossible, even if they were Xenon – here is the spectrograph of a Xenon bulb which I have printed off from Wikipedia. To be white they need to have a continuously equal emission across the entire visible spectrum but there are clearly missing gaps. This shows that Xenon bulbs should really be considered blue.”

Bill’s jaw drops, has his friend Albert misled him? He doesn’t know what a spectrograph is but it sounds like Charlie knows what he is talking about. “I thought they looked white,” he says, lamely.

“They could not have looked white and I can clearly see the lights on the car are red. Look, I have a spectroanalyser here – you can see all the transmission lines from the lights are in the red part of the spectrum.”

“But they must be white”

“No, red”

“Are you sure?”

“Absolutely.”

“I don’t understand.”

Albert’s neighbour, David, overheard the conversation from his garden next-door. He has often been on journeys with Albert in his car but cannot drive himself, as he is blind.

Even if I had my sight, he mused, I would never be able to understand how cars work. It is clear the experts are still arguing about basic theories and new ones are still being developed. Only last week Charlie had explained that even the cleverest people over the last 300 years, Newton, Bernoulli and Einstein did not understand the principles. It was a pure accident that Albert’s car worked at all because the mathematics that the engineers were using when they designed it were all completely wrong. He was lucky to have Charlie as a friend as he needed someone clever who was keen to explain the visible world to him.

Dear reader, you will have worked out already that the car’s name is “Lift”. Have you worked out if you are an A, B, C or D? (Me? I like to think I am a B, will everyone please tell me if I ever act as a C). Rolo Tamasi 12:32, 15 September 2007 (UTC)

/test