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# Why do airplanes fly? by Lukasz Szymura #scichallenge2017

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Have you ever wondered what keeps them up there?
How do they do it?
Here's how it's done ...
#scichallenge2017

Published in: Science
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### Why do airplanes fly? by Lukasz Szymura #scichallenge2017

1. 1. Author: Łukasz Szymura
2. 2. Have you ever wondered what keeps them up there? How do they do it? Here's how it's done: An aircraft in flight is acted upon by four forces: lift, gravity, thrust and drag. Each of these opposes each other, and balances each other out like this: Lift = Gravity Thrust = Drag What about this flying?
3. 3. What are they and what do they do?  Thrust: It's the force that moves an airplane forward through the air. It's made by a propeller or a jet engine.  Drag: This is the air resistance that tends to slow the forward movement of the airplane.  Gravity: It's the force that pulls all objects towards the earth.  Lift: This is the upward force that is created by the movement of air above and below a wing.
4. 4. Aerodynamic lift When a motor-driven aircraft is moving at high speed, the air moves in the opposite direction according to the principle of relative motion.  The aerodynamic lift is generated by the air movement with respect to the aircraft's profiled wings.  The wing is inclined with respect to the direction of flight at an angle known as the attack angle.
5. 5.  Slope of the wings relative to the flowing air masses  Air flow from both sides of the wings (differential pressure) - Bernoulli's Law  Pumping large amounts of air down through the wings - Coanda effect What affects the aerodynamic lift?
6. 6. Bernoulli's Law How to understand that?  Dynamic pressure depends on fluid velocity.  The air that has a higher velocity, that is, at the top of the wing, will therefore have a lower static pressure than the air at the bottom. The sum of the static pressure (normal pressure) and the dynamic pressure in a given fluid stream (liquid or gas) is constant. How does it work? Let's see examples … 
7. 7. Bernoulli's Law 1st example Slightly bent A4 paper so that it hangs freely down. We strongly blow in the horizontal direction and the sheet floats upward.
8. 8. Bernoulli's Law 2nd example Two lightly bent sheets of A4 paper are held side by side so that they hang vertically downwards. We blow heavily between the sheets and the sheets are getting closer to each other.
9. 9. Bernoulli's Law 3rd example Put a sheet of A4 paper on two piles of books. If we blow strongly under a sheet of paper, the paper bends down.
10. 10. Coanda effect This is a physical phenomenon where a stream of fluid (gas or liquid) tends to adhere to the nearest surface. Let's see how it looks in practice … 
11. 11. Coanda effect - example We hang a ping pong ball on the string. We run a tap. When the ball gets into a stream of water flowing from the tap, it will be drawn into the stream.
12. 12. How do you explain this experiment? The behavior of the ball can be also explained by Bernoulli's law
13. 13. Clarification with Bernoulli’s Law The ping-pong ball stays within the column of air coming from the hair dryer because of air pressure. The air coming from the hair dryer is moving faster than the air around it, and this means that it also has a lower air pressure than the air around it. So the ball is kept within the column of lower air pressure because of the higher-pressure air surrounding it.
14. 14. Summary Airplanes fly because they are able to generate a force called Lift which normally moves the airplane upward. Lift is generated by the forward motion of the airplane through the air. This motion is produced by the Thrust of the engine(s). Enjoy your flight ! 
15. 15. Bibliography: • http://fizyka.net.pl/ciekawostki/ciekawostki_t3.html •http://www.foton.if.uj.edu.pl/documents/12579485/05b73ed7-edd5-4a9a- bfec-b391e6571663 •https://pl.wikipedia.org/wiki/Efekt_Coandy •https://s-media-cache- ak0.pinimg.com/736x/02/b3/cf/02b3cfb158fa110e91f624ff2f3bfbe1.jpg •http://1.bp.blogspot.com/- 6aSrkkS0F6g/U3iCZd9N0II/AAAAAAAANp4/Jh8eaort0ms/s1600/775px- Lift-force-pl.svg.png •http://www.flybangor.com/how-planes-fly •http://www.kids.ct.gov/kids/cwp/view.asp?q=330926 •http://www.physicscentral.com/experiment/physicsathome/ping-pong- physics.cfm