AEROSOLS |
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Aerosol spray is the name given to a type of canister containing liquid under pressure from pressurized vapor in equilibrium with another liquid, which often also dissolves the payload (see propellant below). When the can's valve is opened, the liquid is forced out of a small hole and emerges as an aerosol, or mist. As gas expands to drive out the payload, some propellant evaporates inside the can to maintain an even pressure. Outside the can, the droplets of propellant evaporate rapidly, leaving the payload suspended as very fine particles or droplets. Typical liquids dispensed in this way are insecticides, deodorants and paints. An atomiser is a similar device that is pressurised by a hand-operated pump rather than by stored gas.
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HELICOPTERS |
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A helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors (propellers). Helicopters are classified as rotary-wing aircraft to distinguish them from conventional fixed-wing aircraft. The word helicopter is derived from the Greek words helix (spiral) and pteron (wing). The engine-driven helicopter was invented by the Slovak inventor Jan Bahyl. The first stable, single-rotor, fully-controllable helicopter to enter large full-scale production was made by Igor Sikorsky in 1942.
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