A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation for example, the large muscles of a weightlifter. Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment. Also used to describe the process of genetic change within a population, as influenced by natural selection. A graph of the average fitness of a population in relation to the frequencies of genotypes in it.
While the mixture is still compressed high pressure, high densityan electric spark plug produces a flash that ignites it. The heat from this controlled explosion increases the volume of air, which forces the piston down into the cylinder.
This opens an outlet valve, causing the piston to rise and release exhaust gases. As the piston moves back down again, an inlet valve opens, bringing another burst of gasoline-air mixture into the chamber.
The piston, whose downward stroke closed the inlet valve, now shoots back up, compressing the gas and air to repeat the cycle. The reactions of the gasoline and air are what move the piston, which turns a crankshaft that causes the wheels to rotate.
So much for moving—what about stopping? Most modern cars are equipped with an airbag, which reacts to sudden impact by inflating. This protects the driver and front-seat passenger, who, even if they are wearing seatbelts, may otherwise be thrown against the steering wheel or dashboard.
But an airbag is much more complicated than it seems. In order for it to save lives, it must deploy within 40 milliseconds 0. Not only that, but it has to begin deflating before the body hits it.
An airbag does not inflate if a car simply goes over a bump; it only operates in situations when the vehicle experiences extremedeceleration. When this occurs, there is a rapidtransfer of kinetic energy to rest energy, as with the earlier illustration of a stone hitting concrete. And indeed, if you were to smash against a fullyinflated airbag, it would feel like hitting concrete—with all the expected results.
The airbag's sensor contains a steel ballattached to a permanent magnet or a stiff spring. The spring holds it in place through minormishaps in which an airbag would not be warranted—for instance, if a car were simply to be "tapped" by another in a parking lot.
But in a case of sudden deceleration, the magnet or springreleases the ball, sending it down a smooth bore. It flips a switch, turning on an electrical circuit.
This in turn ignites a pellet of sodium azide, which fills the bag with nitrogen gas. The events described in the above illustration take place within 40 milliseconds—less time than it takes for your body to come flying forward; and then the airbag has to begin deflating before the body reaches it.
At this point, the highly pressurized nitrogen gas molecules begin escaping through vents. Thus as your body hits the bag, the deflation of the latter is moving it in the same direction that your body is going—only much, much more slowly.
Two seconds after impact, which is an eternity in terms of the processes involved, the pressure inside the bag has returned to 1 atm.
The New Way Things Work. Air and Other Gases. Illustrations by Anni Matsick. Twenty-First Century Books, The noble gases are an inert group of elements with some fun and fascinating uses. This lesson will explore the properties that the noble gases share and will look at some of their uses.
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The other noble gases are present in such small amounts that it is usually more convenient to express their concentrations in terms of parts per million (ppm).
The concentrations of neon, helium, krypton, and xenon are, respectively, 18 ppm, 5 ppm, 1 ppm, and ppm.
CONCEPT. Gases respond more dramatically to temperature and pressure than do the other three basic types of matter (liquids, solids and plasma). For gases, temperature and pressure are closely related to volume, and this allows us to predict their behavior under certain conditions. noble - Traduzione del vocabolo e dei suoi composti, e discussioni del forum.
Acronym expansions, definitions, links, and opinions. Click here for bottom) No Chemical element abbreviation for Nobelium, At. No. , a transuranide element and perhaps the most blatant bid for a Nobel prize in the history of chemistry.