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23 Cards in this Set
- Front
- Back
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Atmospheric Pressure
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The pressure exerted against bodies immersed in the atmosphere. It results from the weight of air pressing down from above. At sea level, atmospheric pressure is about 101 kPA.
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Barometer
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Any device that measures atmospheric pressure.
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Boyle's law
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The product of pressure and volume is constant for a given mass of confined gas, as long as temperature remains unchanged
P1V1= P2V2 |
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Archimedes' Principle for air
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An object surrounded by air is buoyed up with a force equal to the weight of displaced air.
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Bernoulli's Principle
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The pressure in a fluid moving steadily without friction or outside energy input increases when the fluid velocity increases
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Plasma
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An electrified gas containing charged atoms (ions) and free electrons. Most of the matter in the universe is in the plasma phase.
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1. Distinguish among gas, a liquid, and a fluid
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gases flow as well as liquids flow, so they are both called fluids. The difference is that the distance between the molecules is greater in gas and free from cohesive forces than that of liquid and solid phases.
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Atmosphere
What is the energy source for the motion of gas in the atmosphere? What prevents atmospheric gases from flying off into space? |
The sun, gravity
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Atmosphere
How high would you have to go in the atmosphere for half of the mass of air to be below you? |
5.6 kilometers or (18,000 ft)
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增員
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증원
an increase of the staff[personnel]; |
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What is the approximate mass of a column of air 1 cm^2 in area that extends from sea level to the upper atmosphere? What is the weight of this amount of air?
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At sea level, 1 cubic meter of air has a mass of about 1 1/4 kilograms. About 10 Newtons
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What is the SI unit of atmospheric pressure?
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Pascal at sea level it is
(101.3 kPa) |
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What is the pressure at the bottom of the column of air discussed in question 6?
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10 N/cm^2
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Boyle's Law
By how much does the density of air increase when it is compressed to half its volume? |
It doubles, so pressure is proportional to density
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What happens to the air pressure inside a balloon when it is squeezed to half its volume at constant temperature?
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The air density is doubled and so too the pressure
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What is an ideal gas?
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An ideal gas is one in which the disturbing effects of the forces beween molecules and the finite size of the individual molecules can be neglected. Air and other gases under normal pressures approach ideal gas conditions where Boyle's law applies P1V1=P2V2
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A balloon that weighs 1 N is suspended in air, drifting neither up nor down. How much boyant force acts on it? What happens if the buoyat force decreases? If it increases?
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a displaced weight of fluid queial to its own weight. Air being the fluid. air pressure acting up against an object immersed in air is greater than pressure above pushing down. Archimede's principe for water works for air, an object surrounded by air is buoyed up by a force equal to the weight of the air displaced.
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Does the air exert buoyant force on all objects in air or only on objects such as balloons that are very light for their size? Why does the air support only things with a very low density?
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any object that has a mass less than the mass of an equal volue of air which is 12 newtons. Any object less dense than air will rise in ari.
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What usually happens to a toy helium- filled balloon that rises high into the atmosphere?
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It will rise only so long as it displaces a weight of air greater than its own weight. Since air becomes less dense with altitude a lesser weight of air is displaced per given volume as the ballon rises. So When the weight of displaced air equals the total weight of the balloon, upward acceleration of the balloon will cease.
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Bernoulli's principle
What happens to the internal pressure in a fluid flowing in a horizontal pipe when its speed increases? |
when the speed of fluid increases, the internal pressure decreases.
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What are streamlines? Is the pressure greater or less in regions where sreamlines are crowded?
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streamlines are the smooth paths, or trajectories of the bits of fluid. they get closer in narrower regions and farther apart in wide areas. Where the flow speed is greater and the pressure within the fluid is less. This principle only holds for steady flow
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Plasma
How does a plasma differ from a gas? |
It is an electrified gas, it readily conducts electric current, absorbs certain kinds of radiation that pass unhindered through a gas and can be molded and shaped and moved by electric and magnetic fields.
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a) i what sense is a plasma electrically charged? (b) In what sense is a plasma electrically neutral?
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In the atoms and molecules it is charged but as a whole it is neutral beecause theere are still equal numbers of positive and negative charges.
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