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Everything is made up of elements Modern elements are less evocative but more numerous, they make up just over one hundred basic substances All things consist of particles called atoms The way molecules behave governs the workings of many machines, such as ships, airplanes, pumps, refrigerators, and combustion engines. Molecules of gases are so hyperactive that they will fill any space open to them In liquids, the molecules are less energetic and go haphazardly around in small groups In a solid, the molecular bonds are strong and hold the molecules firmly together so that the solid is hard and rigid. Heat is a form of energy The point at which all heat vanishes is called absolute zero The atoms of elements are made up of even smaller particles electrons, which form the outer shells of each atom, and protons and neutrons, which make up its nucleus Water does move out of the way when any thing enters it. But rather than leaving nothing below an immersed object, the water around it pushes back and tries to support the object. If the water succeeds, the object floats. Upthrust increases as more and more of the raft settles in the water.
At some point, the upthrust becomes equal to the weight of the raft and the raft floats. The density factor, rather that weight, determines whether things float or sink The density of an object is equal to its weight divided by its volume By adjusting the amount of water in the tanks, a submarine s weight and buoyancy can be precisely regulated All powered craft that travel in or on water move by imparting movement to the water or air around them and they steer by altering the direction in which the water or air flows The loading of a ship is regulated by marks on the side of the hull. The lines indicate loading limits for a variety of seas and seasons. Principles of propulsion and heavier than air flight are: 1. Action and reaction, and: 2.
Suction The sail is able to propel the boat at any angle to the wind except head-on. They do this by moving in a zig-zapping pattern to keep the sail always at an angle to the wind A yacht usually has two triangular sails the mainsail and the jib An airship has a vast envelope that creates a powerful upthrust to lift the substantial weight of the cabin, engine, fans, and passengers The bulk of the envelope contains helium, a light gas which reduces the weight of the airship, so that it is equal to the upthrust, thereby producing negative buoyancy. Inside the envelope are compartments of air called ballonet's. Pumping air out of or into the ballonet's decreases or increases the airships weight and it ascends or descends A hot-air balloon has no means of propulsion and drifts with the wind The airfoil is curved so that air passing above the wing moves faster than air passing beneath In order to steer an airplane, a system of flaps is used. These act just like the rudders of a boat deflecting air flow and turning or tilting the airplane so that it rotates around its center of gravity.
By adjusting the area of the flaps presented to the air, and their angle to it, a pilot is able to vary the amount of lift generated by the wing There are four basic kinds of flaps. Leading-edge flaps, trailing edge flaps, which extend the entire length of the wing to provide more lift and drag, spoilers, and ailerons The helicopter moves only the rotor blades to provide lift. As they circle, the blades produce lift to support the helicopter in the air and also move it in the required direction A helicopter is powered by a gasoline engine or a gas turbine similar to a jet engine. The engine drives the rotor shaft whereupon action and reaction come into play Large helicopters often have two main rotors to give double the lift of a single main rotor and raise a heavy load or more passengers Propellers and jet engines move air backward at high speeds and this pushes back to force the aircraft forward By using the downward thrust of its jet engine, the jump jet can dispense with the need for a runway and take-off vertically from the ground An airfoil works better in water, which is denser than air and therefore gives more lift at lower speed Frees from friction with the water, a hydrofoil can skim over the waves at two or three times the speed of the fastest floating boats
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Research essay sample on Water Or Air Action And Reaction Weight
