How to make a screen capture with android??

It depends on the version of android that you:
- For android 4.0, 4.1, 4.2, press the button "on / off" and "Down" at the same time, until the image is saved to your gallery
- For android 2.2 (froyo), press the "back" button and "on / off" at the same time
- For android 2.3 (gingerbread), press the "home" button and "on / off" at the same time
- For android 3 (honeycomb), it is your rooter machine, which depends on the exact model. Search "root model" in google.

In all cases, you can also install an application (free) to make copies as Wallpaper "No Root Screenshot It" or "Screenshot UX". In some cases (it depends of the model), it may be you need to initialize your android with an application that runs on your PC / MAC (this is explained in the manual of the android applications).

how airplanes fly

Air is a physical substance which has weight. It has molecules which are constantly moving. Air pressure is created by the molecules moving around. Moving air has a force that will lift kites and balloons up and down. Air is a mixture of different gases; oxygen, carbon dioxide and nitrogen. All things that fly need air. Air has power to push and pull on the birds, balloons, kites and planes. In 1640, Evangelista Torricelli discovered that air has weight. When experimenting with measuring mercury, he discovered that air put pressure on the mercury. 

Francesco Lana used this discovery to begin to plan for an airship in the late 1600s. He drew an airship on paper that used the idea that air has weight. The ship was a hollow sphere which would have the air taken out of it. Once the air was removed, the sphere would have less weight and would be able to float up into the air. Each of four spheres would be attached to a boat-like structure and then the whole machine would float. The actual design was never tried.
Hot air expands and spreads out and it becomes lighter than cool air. When a balloon is full of hot air it rises up because the hot air expands inside the balloon. When the hot air cools and is let out of the balloon the balloon comes back down.

Diagram of how air flows over and under airfoilHow Wings Lift the Plane

Airplane wings are curved on the top which make air move faster over the top of the wing. The air moves faster over the top of a wing. It moves slower underneath the wing. The slow air pushes up from below while the faster air pushes down from the top. This forces the wing to lift up into the air.

Laws of Motion

Sir Isaac Newton proposed three laws of motion in 1665. These Laws of Motion help to explain how a planes flies.
  1. If an object is not moving, it will not start moving by itself. If an object is moving, it will not stop or change direction unless something pushes it.
  2. Objects will move farther and faster when they are pushed harder.
  3. When an object is pushed in one direction, there is always a resistance of the same size in the opposite direction.

Forces of Flight

Four Forces of Flight
Lift - upward 
Drag - down and backward
Weight - downward
Thrust - forward
Picture of plane with four forces

Controlling the Flight of a Plane

How does a plane fly? Let's pretend that our arms are wings. If we place one wing down and one wing up we can use the roll to change the direction of the plane. We are helping to turn the plane by yawing toward one side. If we raise our nose, like a pilot can raise the nose of the plane, we are raising the pitch of the plane. All these dimensions together combine to control the flight of the plane. A pilot of a plane has special controls that can be used to fly the plane. There are levers and buttons that the pilot can push to change the yaw, pitch and roll of the plane.
To roll the plane to the right or left, the ailerons are raised on one wing and lowered on the other. The wing with the lowered aileron rises while the wing with the raised aileron drops.
Pitch is to make a plane descend or climb. The pilot adjusts the elevators on the tail to make a plane descend or climb. Lowering the elevators caused the airplane's nose to drop, sending the plane into a down. Raising the elevators causes the airplane to climb.
Yaw is the turning of a plane. When the rudder is turned to one side, the airplane moves left or right. The airplane's nose is pointed in the same direction as the direction of the rudder. The rudder and the ailerons are used together to make a turn

How does a Pilot Control the Plane?

Picture of plane with ailerons identifiedPicture of plane with rudder identifiedPicture of Plane with elevators identified
To control a plane a pilot uses several instruments...
The pilot controls the engine power using the throttle. Pushing the throttle increases power, and pulling it decreases power.
Picture shows plane rolling
Left: Picture of plane in roll
The ailerons raise and lower the wings. The pilot controls the roll of the plane by raising one aileron or the other with a control wheel. Turning the control wheel clockwise raises the right aileron and lowers the left aileron, which rolls the aircraft to the right.
Pioture shows the areas of the plane used to control the Yaw
Right: Picture of plane Yaw
The rudder works to control the yaw of the plane. The pilot moves rudder left and right, with left and right pedals. Pressing the right rudder pedal moves the rudder to the right. This yaws the aircraft to the right. Used together, the rudder and the ailerons are used to turn the plane.
Picture shows the direction of the plane's pitch
Left: Picture of Plane Pitch
The elevators which are on the tail section are used to control the pitch of the plane. A pilot uses a control wheel to raise and lower the elevators, by moving it forward to back ward. Lowering the elevators makes the plane nose go down and allows the plane to go down. By raising the elevators the pilot can make the plane go up.
The pilot of the plane pushes the top of the rudder pedals to use thebrakes. The brakes are used when the plane is on the ground to slow down the plane and get ready for stopping it. The top of the left rudder controls the left brake and the top of the right pedal controls the right brake.
If you look at these motions you can see that each type of motion helps control the direction and level of the plane when it is flying.

Sound Barrier

Sound is made up of molecules of air that move. They push together and gather together to form sound waves . Sound waves travel at the speed of about 750 mph at sea level. When a plane travels the speed of sound the air waves gather together and compress the air in front of the plane to keep it from moving forward. This compression causes a shock wave to form in front of the plane.
In order to travel faster than the speed of sound the plane needs to be able to break through the shock wave. When the airplane moves through the waves, it is makes the sound waves spread out and this creates a loud noise or sonic boom. The sonic boom is caused by a sudden change in the air pressure. When the plane travels faster than sound it is traveling at supersonic speed. A plane traveling at the speed of sound is traveling at Mach 1or about 760 MPH. Mach 2 is twice the speed of sound.

Regimes of Flight

Sometimes called speeds of flight, each regime is a different level of flight speed.
ExampleRegimes of Flight
Picture of Seaplane
General Aviation(100-350 MPH).
Most of the early planes were only able to fly at this speed level. Early engines were not as powerful as they are today. However, this regime is still used today by smaller planes. Examples of this regime are the small crop dusters used by farmers for their fields, two and four seater passenger planes, and seaplanes that can land on water.
Picture of Boeing 747
Boeing 747
Subsonic (350-750 MPH). 
This category contains most of the commercial jets that are used today to move passengers and cargo. The speed is just below the speed of sound. Engines today are lighter and more powerful and can travel quickly with large loads of people or goods.
Picture of Concorde Jet
Supersonic (760-3500 MPH - Mach 1 - Mach 5).
760 MPH is the speed of sound. It is also called MACH 1. These planes can fly up to 5 times the speed of sound. Planes in this regime have specially designed high performance engines. They are also designed with lightweight materials to provide less drag. The Concorde is an example of this regime of flight.
Picture of Space Shuttle
Space Shuttle
Hypersonic (3500-7000 MPH - Mach 5 to Mach 10).
Rockets travel at speeds 5 to 10 times the speed of sound as they go into orbit. An example of a hypersonic vehicle is the X-15, which is rocket powered. The space shuttle is also an example of this regime. New materials and very powerful engines were developed to handle this rate of speed. 

The History of the Printing Press

Throughout the past 4000 years, record keeping has been an integral part of human civilization.
Record  keeping,  which  allows  humans  to  store  information  physically  for  later  thought,  has
advanced  with  technology.  Improvements  in  material  science  improved  the  writing  surface  of
records,  improvements  with  ink  increased  the  durability  of  records,  and  printing  technology
increased the speed of recording. One such printing technology is the printing press, an invention
that allowed mass production of text for the first time. The printing press has influenced human
communication, religion, and psychology in numerous ways.

The printing press was invented by  Johannes Gensfleisch zur Laden zum Gutenberg, born to a
wealthy merchant family in 1398 in the German city of Mainz. He studied at the University of
Erfurt in 1419. Later in his life, in 1448, using a loan from his brother-in-law Arnold Gelthus, he
began developing a moveable type printing press. By 1450, the Gutenberg printing press was in
full  operation  printing  German  poems.  With  the  financial  aid  of  Johann  Fust,  Gutenberg
published his 1282 page Bible with  42 lines per page. This bible, more commonly known as the
Gutenberg  Bible,  was  considered  the  first  mass-produced  book  in  history  because  180
 copies were printed. (―Gutenberg, Johann,‖ n.d., para. 1-4).

The  printing  press  was  first  brought  to  England  by  William  Caxton.  In  1469,  Caxton
learned  how  to  use  the  press  in  order  to  sell  books  to  the  English  nobility.
The  first  book  he printed, his own translation of the History of Troy, had great success and
enabled him to craft his own printing press in Michaelmas, England in 1476. The first piece
of English printing, A Letter of Indulgence  by John Sant, was printed with this press,
thus ushering in a new era for English literature.

Printing  technology  was  brought  to  America  almost  two  centuries  later.  British  settlers  often
established printing presses to provide spiritual texts for colonists; thus, it is no surprise that a
printing press was brought to Cambridge, Massachusetts in 1638. Printers often produced their
own paper using the same techniques that were used in England. In 1690, William Rittenhouse
(Rittenhausen),  a German printer who learned fine Dutch paper making practices, revolutionized
American  printing  when  he  established  the  first  American  paper  mill  in  Germantown,
Pennsylvania. Printers now had access to cheaper paper and had more time to work on their trade
(On printing in America, n.d., para. 3).

Even after the news of Gutenberg‘s invention spread to other European countries, people
did not adapt quickly to the new printing style. In the fifteenth century, literacy was confined to a
small elite group that was wealthier than others. With a small percentage of people who could
read, the demand for books was relatively small. The practice of hand-copying books, which was
done for centuries by monks and scalars, produced a very low output of expensive books  with
many mistakes. Still, the early printing press was slower and more expensive than hand-copying;
therefore, written word was preferred as a relatively cheap, portable, and rapid method of storing
and transmitting information (Volti, n.d., para. 1-6).

Basic Science and Technology
The printing press clearly relies on a medium that allows the printer to record using ink.
Dating back to 15,000 B.C.E., humans have recorded on surfaces such as cave walls, tree bark,
stone,  clay,  wood,  wax,  metal,  papyrus,  vellum,and parchment, and  paper. However,  printers
were constantly searching for new materials because many of these surfaces were not sufficient.
For example, cave paintings, in which pictures  were drawn on cave walls, were impossible to
transport and difficult to see without light. Papyrus (compressed sheets of Egyptian reed stalk),
as well as vellum and parchment (the prepared skin of cow, lamb, goat, and sheep), were high in
cost and deteriorated quickly. Clay, which dries fast, was difficult to use (―Paper,‖ n.d., para. 1).
At the end of the seventeenth century, it was necessary that printers begin exploring other
sources of paper because the worldwide production of paper lagged behind the capability of the
printing  press.  Previous  to  this  time,  the  methods  to  produce  pape were very similar  to the
methods  used  in  ancient  China  because  paper  producing  technology  was  adequate  for  the
demand. When the printing press became popular in colonial America, the mass production of
newspapers  led  to  paper  shortage.  In  order  to  remedy  this  problem,  linens  from  mummy
wrappings  were  imported  from  the  East.  Mummy wrappings and rags were  mixed and turned
into pulp to create mummy paper. On average, the linens from a single mummy could supply two
average seventeenth  century Americans for a year. Although this source nullified the scarcity of
paper,  it  had  non-ideal  qualities  such  as  brown discoloration, oils, and botanical  residue;  in
addition, this source angered archeologists and decreased in supply (Wolfe, 2004, paras. 1-3).
The most effective paper is made from pulped plant fiber. Originating from China in 105
A.D., plant fiber from the mulberry tree was used to make paper (―Paper,‖ n.d., para. 2). When
the process spread to Europe from the Arabs in the sixteenth  century, Europeans used the pulp of
cotton and linen rags because they were available in large quantities. Although these people used
different materials than the Chinese, the cloth was turned into a pulp and made into paper using a
method similar to the ancient Chinese method. Beginning in 1850, paper producers began to use
wood as the primary source of plant fiber because it was abundant. However, wood grinders at
the time were not effective enough to produce pulp: there were often solid chunks of wood which
led to low quality paper. On the other hand, the quality of wood pulp paper was still better than
the  quality  of  rag  pulp  paper.  As  grinding  machines  advanced,  the practice of manufacturing
wood pulp paper became more refined  and efficient.  In modern times,  most paper mills  grind
wood into pulp and then apply a chemical process that uses steam along with sodium hydroxide
(NaOH) and sodium sulfide (Na2SO3) to digest the wood chips to produce a finer pulp
 (―Paper,‖ n.d., para. 7).

As  the  population  became  more  literate  and  the  newspaper  became  more  popular  into
mid-eighteenth century, the demand for printed material skyrocketed. Printers could now make
more money by printing faster. Because the population was interested in current news, there was
a need  for printers to devise a technique to print the news faster. The first breakthrough came in
1812 when Friedrich Koenig and Friedrich Bauer invented the steam-powered press. This press
was  able  to  print  1,100  newspapers  per  hour,  approximately  four  times  the  speed  of
 manual presses.  The  greatest  printing  press  improvement  came  from  Richard  Hoe  in  1847
  when  he engineered a rotary printing press. Instead of laying movable type on a flat bed, the type
 was set onto the outside of a large cylinder. Paper was then placed on a flat bed. When the cylinder
 was rotated, paper would feed into the machine with high pressure between the flat bed and cylinder,
thus allowing contact for the ink to be imprinted onto the paper. This inventory further improved
the press, called the Hoe press or lightning press, by adding another cylinder. In addition, using
even more cylinders, Hoe devised a machine that could print of both sides of a continuous piece
of paper patented by France's Nicholas Louis Robert in 1798.

Language  is  another  important  consideration  to  printing.  Printers  who  used  moveable
type printing presses had to hand lay each letter that they wanted to print; thus, the printer needed
to cast each letter to be able to print. Moreover, the same letter was often used mu ltiple times for
each press indicating that it is necessary to cast many of the same letters. A language with more
letters,  such  as  Chinese,  requires  a  vaster  base set of letters compared  to a language  such  as
English. Movable type for languages that have fewer letters is easier to replace and manufacture.
In countries such as China, hand-copying was much more effective than the printing press until
the press became much more advanced (Printing, 2009, Original letterpress plates section, para. 3).

Impact of the Printing Press on History
The  printing  press  influenced  communication  in  numerous  ways.  Before  the  printing
press, explorers could only record manually. Because it was very expensive to have many books
copied,  maps  were  very  scarce;  therefore,  the  information  discovered by mapmakers was not
used often. When it became cheaper to print, explorers were able to share their information with
others, thus allowing increased education and easier navigation. The printing press also allowed
scientists of all fields to compare their findings with others. Scientific theories started to form on
a large scale because more supportive evidence  was accessible.  In mathematics, a  field which
relies heavily on uniform systems, mathematicians were able to build upon other works as they
became available. All people were able to educate themselves better with more accessible and
affordable text. Also, scientists were able to spend more time thinking about scientific concepts
and less time copying previous research. The printing press  clearly influenced  communication
(Volti, n.d., para. 1-3).

Religion was impacted by the printing press in several ways. As the amount of written
communication increased, ideas spread easily. Religious ideas were no exception. Martin Luther,
the leader of the protestant reformation, utilized print technology in order to spread his views.
The Christian church had no control over the spread of such religious ideas. To halt the spread of
these ideas, the Church would have to bring to a standstill the production of all printing presses.
However, this would mean halting the printing of the Bible, a message that the Church did not
want  to  send.  In  order  to  read  the  Bible,  many  people  became  literate.  It  is  evident  that  the
printing press affected religious movements (Volti, n.d., para. 7-9).

The printing press has influenced psychology in several major ways. Before the printing
press, people were apt to believe that the text they were reading was true because only the most
noteworthy information was recorded. Since the printing press became popular at the end of the
eighteenth  century,  everything  from  medical  textbooks  to  treaties  on  astrology  were  widely
distributed.  With  so  much  original  research  circulating,  it  is  no  surprise  that  much  of  it  was
People  became  less  willing  to  accept  the  judgment  of  a  single  individual  or  a group
of  individuals.  As  a  result,  a  more  critical  approach  to  understanding  emerged.  The
printing of newspapers also impacted the psychology of people worldwide. The farther away that
a reader was to a newspaper printing business, which were often located in cities, the more time
it would take to get a newspaper. When newspapers first came out, travel was relatively slow;
thus, it took even longer to get a newspaper. People lived closer to cities in order to improve their
access to newspapers. Thus, urbanization increased. In addition, a culture based on print media
was more individualistic than a culture based on collective means of communication. Because
the  printing  press  caused  a  movement  away  from  the  church,  people  had  less  collective
communication  and  more  individual  thought.  The  printing  press  brought  about  fundamental
change in the psychology of educated people (Volti, n.d., para. 4).