IMPACT OF AIR

WE CAN NOT SEE AIR, BUT it is not just   empty space .Air   is a mixture of many gases.Air exerts   pressure   on us,but does not crush us .In principle ,we   are living on the floor of a kilometer -thick   ocean of air   known as the air cover or the atmosphere of the Earth.Since ,air is a matter ,it can also carry   things ;leaves, in autumn ,birds,aircraft,hot air balloons,and many more things .However   ,all objects need   propulsion   to   lift from the ground-birds beat their wings,
Aircraft depends on propellers    or jet engines.
FLYING OF AIRCRAFT-     Air crafts need a combination   of procedures to     fly in the   air .They need   a propulsion   system- a propeller or jet engine .They   also need a lift , which comes   from wings .While flying , the forward thrust causes    the    air   to flow    at great speeds along   the   wings.The   curved shape of the wings and their slightly   tilted    position give rise to   a low pressure   above the aircraft   and high pressure   below it ..This is how the aircraft   is pushed upwards .The pressure difference thus generates a buoyancy ,which is greater than the weight of the aircraft ,which pulls it down .The aircraft will fall    if the buoyancy    is less.
HOT AIR BALLOON   FLOATS IN THE AIR.- Air at 90 degree centigrade filled in the hot air balloon .The hot air keeps the   balloon   in the air    because its   density    is lower than   that of the surrounding    cold air .Before   starting the balloon , a gas burner   is ignited   below the opening   of the huge balloon cover and the flames    heats up the   air in the balloon .When the balloon   is rises   to the desired   height , the burner is switched off, if one   wants to the further ,   it is started again .The balloon must have   a   minimum size so that it can over come the force of    gravitational attraction   of the Earth.Thus hot air balloon   are able to float in air .
PROPELLER    WORKS BY SCOOPING AIR. A    PROPELLER, IN     an aircraft scoops air , as it   scoop water in a ship., as in a wind mill,the blades of   a propeller   are arranged in the form of a star   around   a rotating shaft..They are shaped and aligned   in such a way that the air falls diagonally on them   and flows along them .This create a strong   air flow   that   gives the aircraft the required thrust..This principle is used not just by   smaller aircraft   but also by hovercrafts which can travel over meadows or frozen    water.
CANDIES   ARE SERVED BEFORE AN AIRCRAFT TAKES OFF.-This is because when   an aircraft takes off ,some passengers   experience a crackling sound in the Ears or   get earache .The reason   is that the   inner   ear does    not   adapt itself   quickly   to the lower air pressure caused by the take off.A simple candy   helps   in avoiding this discomfort because while sucking a candy , we need to swallow often .This helps the   small muscles to   expand   the connection between the ear   and the nose .In a way , they are ventilated. This leads to   a quicker adaption   of the inner    ear to the outer air   pressure   and reduce the pain.
WE ARE NOT CRUSHED BY THE AIR PRESSURE.-The air exerts pressure on us .The reason why we are not crushed   by the air pressure    is that    the same air pressure   is also present in the hollow   cavities of our body :in the lungs and in the tiny chambers   of   our bones.With the same pressure in   and around us , we do not feel   the weight of the air at all.
FACTS- The normal aircraft cannot fly in outer space .Because there is no air   in space to generate   lift on   the wings   there will be   no buoyancy   to overcome   the force of   gravity acting downwards.