Category Kids Queries

Helicopters rely on the same forces – thrust and lift – that propel planes miles into the sky. And helicopters have wings just like planes, except, in their case, the wings aren’t fixed o the fuselage (which is why planes are also called fixed-wings are on the propellers – or “rotors” – that whirl above the whirlybird. The helicopter’s engine spins the rotors, which thrusts them through the air and creates lift, pulling the helicopter vertically into the air. The pilot can control the shape (or “angle of attack”) of the rotors to control the amount of lift, as well as angle them forward or backward to determine the direction of flight. The smaller tail rotor, meanwhile, counteracts the rapid spin of the main rotor so that the helicopter doesn’t whirl out of control (the tail rotor also controls turns). Balancing these rotor systems takes some serious multitasking skills and hand-eye coordination (helicopters are trickier to fly than airplanes), but then “rotary-wing aircraft” are much more nimble in the air, able to take off vertically, hover, and dart in any direction.

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Now you know that flying machines need thrust and lift to get off the ground. Lacking engines, gliders must make up for their lack of thrust by maximizing lift. They have skinny bodies and sprawling wings constructed of ultralight materials. These massive wings provide more lift with less air moving over them than conventional plane wings. Glider pilots seek out “thermals,” columns of heated air that rise up from the ground. Thermals are invisible, but they typically form over dark patches of terrain – parking lots or dirt fields. The pilots circle inside the column, letting the heated air push them higher and higher, until they reach the desired altitude. Then they leave the column and glide slowly back to the ground. Glider pilots can also simulate thrust by flying into strong winds.

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Planes soar with the greatest of ease because of two forces: thrust and lift. Thrust is generated by the engines, which use either propellers or jets to propel the plane forward. That forward motion moves air over the wings, which are shaped so that air passes faster over their tops than bottoms. The slower-moving air below the wings creates higher pressure than the faster-moving air below the wings creates higher pressure creates lift, pushing the wings up. As long as a plane has thrust to propel air over the wings, it has lift. If a plane loses thrust, the wings “stall” and the plane plummets.

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Helium balloons float for the same reason a beach ball floats in water. The balloon and the air inside it weigh less than the equivalent amount of water around it. As a result, the beach ball displaces the water surrounding it, pushing it away as it rises to the surface – a concept known as buoyancy. The same thing happens with a helium balloon. Helium is a special gas that weighs less than the surrounding air: Just like the beach ball in the water, the helium balloon pushes away the surrounding gas and rises above it.

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Hot-air balloons are the oldest type of flight technology (pre-dating the airplane by more than 120 years) for a reason: the principle behind “lighter-than-air” flight is simple. Heated air expands, becoming less dense – or lighter – than cool air, which is why hot air rises and cold air falls. Hot-air balloons carry a heat source (typically a flame) that warms the air inside the balloon is lighter than the air outside of it, and the balloon takes flight.

To keep floating, the pilot continues to fire the burners to keep the air inside the balloon hot. To land, the pilot lets the air inside the balloon cool. When this happens, the molecules slow down and take up less space. The air inside the balloon is no longer less dense than the air outside. The balloon sinks towards the ground. So hot air balloons float because hot air is less dense than cold air.

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Thomas Edison is famous for inventing the light bulb in 1878 in New York, USA. Thomas Edison didn’t invent electricity – a natural form of energy that humans have known about since the time of the ancient Greeks – but he did figure out how to harness it to light a filament in a light bulb as well as transmit it to homes through a grid system of wires. A genius tinkerer, Edison also invented the phonograph, a machine that records sounds and plays music (think it as the great-granddaddy of your MP3 player).

Although Thomas Edison gets credit for inventing the light bulb, a draftsman name Lewis Howard Latimer had a bright idea that revolutionized electric light. Latimer’s carbon filament – the fiber inside the bulb that glows when charged with an electric current – styled it for much longer than Edison’s quick-to-burn-out paper filament.

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