Naazima wrote:Marshall,Watson thanks so much.Sorry to trouble you but please tolerate me as I am a beginner.Now,why doesn't a water bottle (full of water) get crushed due to atmospheric pressure if we say that atmospheric pressure is more than water pressure.I will be very grateful to you for clearing my concepts.
Hi Naazima, I'm guessing you live in the Usa and so are comfortable with traditional units like inch, pound, pint...
Let us know if you prefer metric units.
The pressure exerted by a fluid depends on the weight of what's directly above a typical bit of surface area.
So if you go outside and draw a little one-inch square on the sidewalk, there is about 15 pounds of air above that bit of area, bearing down on it.
The nice thing about fluids (i.e. gases and liquids, air and water for instance) is that they *communicate* pressure. So even if you are indoors with a roof over your head you get the same air pressure as the patch of sidewalk under the open sky. As long as there is a window open, for air to flow, the pressure indoors and outdoors is going to equalize.
And the pressure equalizes in all directions. The air in a room presses about equally up underneath a table as it presses down on top of the table. You can think of that as happening because air FLOWS. (It's a fluid and that's what fluids do.)
The pressure in water works roughly the same way. When you are swimming, if you dive down under the water you feel the pressure in your ears. The deeper you go the more pressure you feel.
Basically it is the weight of the water above a typical square inch area+ plus the weight of the air above that. The weight of the fluid bearing down on it.
If you fill an ordinary pint jar with water, the pressure exerted by the water does not amount to much because it's not very deep. It does not amount to much more at the bottom of the jar than it does at the top---where the pressure is merely the air pressure at the surface.
If you were small enough to go swimming in a pint jar of water you would not feel much pressure in your ears when you swam down to the bottom of the jar. You might not feel any pressure difference---it would be to small to feel.
So think about it some. It might become clear. You can always ask more questions. But it might become clear to you just by thinking about it.