For reasons of fuel economy, large civil transport aircraft have to fly at altitudes far in excess of those capable of sustaining life. Whereas 5,500 m is about the maximum altitude at which a person can live for any extended period, a subsonic passenger jet has the best fuel economy when flying at around 12,000 m.
Aircraft manufacturers therefore, have no choice but to pressurize the interior of a passenger aircraft. This poses huge technical problem. At 12,000 m, where the pressure is about one-fifth of that at sea level, the pressure inside is trying to burst the fuselage apart. This pressure has to be contained and all the stretching and flexing of the fuselage during a flight has to be kept within safe limits.
It is far easier to do this – if the pressure differential between inside and outside is kept to a minimum, a cheaper and lighter fuselage structure can be used.
For civil airliners this means that the pressure inside during cruising is kept at the lowest possible safe level – 2500 m. This is about the maximum altitude which a normal healthy person can be subjected to without ill effects.
Even so, unfit people, those with respiratory illness and those who have sampled a few too many duty-free drinks might still feel ill, even at this altitude.
There is another problem: all airfields are not at the same altitude. In an extreme case, a flight from Heathrow in England to La Paz in Bolivia would entail going from sea level to around 5200 m, where the air pressure is about half that at sea level. Under these circumstances it is just not possible to maintain the same pressure throughout the flight. Imagine what would happen if the pressure inside and outside were not the same at the time the doors were opened: the effect would be quite spectacular and most undesirable.
As for the ear popping, nowadays, for your safety and comfort the internal pressure is imperceptibly reduced, all under computer control, as the aircraft climbs. It is gradually increased during descent so that, as the aircraft is coming to a stop on the runway, the pressure inside and out is the same. This is normally sufficient for your ears to adjust, but if all else fails, pinch your nose and gently but firmly increase the pressure in the nasal cavity until you feel the pressure equalize.
and campaign The army normally flies the flag of the headquarters, formation, or other unit at the headquarters building and the commander’s residence. The national flag is displayed at all posts for ceremonies in connection with Republic Day and Independence Day.The Indian war flag is red with the golden lions of Sarnath, and golden crossed swords. The flag of Chief of the Army Staff of the Indian Armed Forces is red in colour with the national flag in one corner, the golden Loins of Sarnath and golden crossed swords. Field Marshals have red flags with crossed batons surrounded by a lotus flower wreath. The Asoka Lion’s emblem is above the wreath, and there are five stars below, all in yellow. The army also has different badges for different regiments, as well as gallantry medals.
A national flag reminds its citizens where they came from, where they are and their duty to the future. It is well known across the length and breadth of the country, and inspires patriotism in its citizens, for it is steeped in history and tradition.
Yes they do. White is associated with peace and honesty. Yellow is a symbol of generosity and red represents bravery, strength and velour. 
Blue stands for vigilance, truth and justice, while green are a symbol of hope, joy and divinity. Black sometimes stands for determination. However, a plain black flag is a symbol of mourning. Flags flown at half mast also denote mourning.Our national flag is made up of three colours – saffron, white and green. The saffron stands for courage and sacrifice; the white, for purity and truth; the green for growth and auspiciousness. In the centre of the white band there is a wheel in navy blue to indicate Dharma Chakra. It is a Buddhist symbol dating back to 200 BC.You must always show respect to the flag, and never use it for anything else except as a symbol of our great nation and culture.
also wear a badge when he goes to work. A badge is something that you wear to show who you are, to which institution you belong, or what your rank is. It may also be reward for something you have achieved, or a sign of your authority.Badges are of great importance in the military. Everyone wears one to show his or her rank, and also signify any special training received and record note worthy achievements. Policeman wears badges to show their authority, and members of a club may wear a badge to show that they belong to a particular club or group. Sometimes badges are worn as a sign of protest, and sometimes as sign of mourning, like the black badges worn when someone dies Badges can be made of many different types of materials… cloths, metal, plastic, rubber or leather. Some badges are quite beautiful and collecting badges can be an enjoyable hobby. 
always given respect. Flags are important in the military where they are used to coordinate actions of different units and avoid confusion. A ship at sea flies a flag to identify itself, and the navy uses flags extensively for signaling Originally, flags were used primarily in warfare. To some extent, they remain a symbol of leadership, serving for identification of friend and foe, and as rallying points. Flags are now also extensively used for signaling, for decoration, and for display. A person who is chosen to carry a flag during any ceremony is called a flag bearer. It is a great honour to be selected as a flag bearer, whether it is your school flag, or the national flag.
Flags have long been used to identify a ship’s nationality and to convey clear messages. Flags of different patterns and colours form an internationally recognized code for the letters of the alphabet and each also has a meaning of its own when flown individually. They are shown below.
directions to people, warn us of dangers, control speed, and enforce traffic rules. Traffic lights are usually placed at the intersection of roads. They indicate when it is safe to drive, ride or walk. Everywhere in the world, a red traffic light means ‘stop’ and green light means ‘go’.Road signs were the first traffic control devices to direct travelers on their journeys. Today, road signs have many different purposes. Some have arrows showing the direction in which to go. Others have a slash inside a circle – a warning that certain vehicles and certain actions are not allowed Road signs also remind us of the speed limit, and give details about the road surface. They tell us when schools, hospitals and petrol bunks are nearby, and indicate dangerous turns on the road. It is important that we all learn the meaning of these road signs and traffic signals, so that accidents can be avoided, and we can have safe and comfortable journrys.
Red Indians, or American Indians, provided a means of communicating their stories, myths and legends. They were generally carved from giant trees, and were made up of an arrangement of symbols.The symbols on the totem pole told a story or recalled an event. These messages and stories tell us a lot about the Red Indians, their culture and their way of life. Some poles were erected to celebrate cultural beliefs; others were just an artistic presentation. Certain poles also contained graves within them. But whatever their purpose, totem poles with their huge size, subdued colours, and intricate carvings covered with magnificent symbols are both awesome and mysterious at the same time.