Pressure in Air
Pressure in Air
Pressure in Air:
Buoyancy in gas acts in the same way as that in a liquid. Objects in a liquid are buoyed upward because the pressure acting up against the bottom of the object exceeds the pressure acting down against the top. Likewise air pressure acting up against an object immersed in air is greater than the pressure above pushing down. The buoyancy in both cases is numerically equal to the weight of fluid displaced. Archimedes principle applies to air just as it does for liquid: When an object is wholly or partially immersed in a gas it loses some of its weight which is equal to the weight of the displaced gas.
Example: How does buoyancy change as a helium filled balloon ascends?
Solution : If the balloon is free to expand as it rises, the increase in volume is counteracted by a decrease in the density of higher-altitude air. So. interestingly, the greater volume of displaced air does'nt weigh more, and buoyancy stays the same. If a balloon is not free to expand. buoyancy will decrease as the balloon rises because of the lesser density of the displaced air. Usually, balloons initially expand when they rise, and, if they dont eventually rupture, fabric stretching reaches a maximum and the balloons settle where buoyancy matches their weight.
Which of the following are correct : (a) Our Earth’s surface is covered with a thick layer of air called the atmosphere. (b) The atmosphere extends up to a height of 200 km. (c) The layer of air becomes thinner and thinner as we go higher up. | |||
| Right Option : D | |||
| View Explanation | |||
Which of the following are correct : (a) Our Earth’s surface is covered with a thick layer of air called the atmosphere. (b) The layer of air becomes thinner and thinner as we go higher up. | |||
| Right Option : C | |||
| View Explanation | |||
Which of the following are correct : (a) When an object is wholly or partially immersed in a gas it loses some of its weight which is equal to the weight of the displaced gas. (b) When an object is wholly or partially immersed in a gas it loses some of its weight which is more than the weight of the displaced gas. (c) Sufficient air for breathing is present only up to about 15 km above the Earth. | |||
| Right Option : C | |||
| View Explanation | |||
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