I am sitting inside a closed room with a cement ceiling just above my head. The pressure of the atmosphere is exerted on the ceiling from above(outside). But solid cement not being a fluid does not transport that pressure into my room. But i still feel the atm pressure which has no way to be transported into the room.I do not boil to death or anything. How does this happen?
[Physics] Pressure inside a closed room
atmospheric sciencepressure
Related Solutions
Yes, atmospheric pressure is primarily caused by the weight of the atmosphere above you. This is why the pressure decreases as your altitude increases.
A fluid (like air) under pressure exerts equal force in all directions while at rest. [Side note: Technically it exerts slightly more force downwards because of gravity. However, this effect is only noticeable on scales much larger than what we are dealing with here, so I ignore this effect in this answer.] So the air at ground level pushes equally on the ground beneath it and the air next to and above it. This is the pressure that you constantly feel. Now imagine yourself in a gazebo - a roof above you, but with open sides. Clearly, the air pushes on you from the sides. But the air above you is also pushing down on you with the same force per area. Why? The air above you is being pushed on the sides, which means it is under the same pressure that you are. It pushes back against the air compressing it from the sides and pushes in the vertical direction, both up, against the roof of the gazebo, and down, against you.
While rooms have walls, they are not airtight, which means that air can flow through them. If the pressure inside the room is different from the pressure outside, air will flow to "balance out" the pressure imbalance. In effect, any room is like a gazebo - the pressure will remain basically the same inside and out if nature/physics/entropy is allowed to run its course.
That being said, if you are willing to do some work, you can change the pressure inside a room - see
http://en.wikipedia.org/wiki/Negative_room_pressure
and
The concept you need to include in your thinking is related to Pascal's Principle. As applied to your question, it means the pressure from the water above a particular position under water does not just act downward. That pressure acts in all directions. So, in effect, pressure in a fluid "moves around corners". When you are under the hypothetical fixed object in your scenario, you feel the pressure from the water to the sides of you. That water feels pressure from the water above as well as to the sides (and bottom) of it. If more water is added, or you and your object are deeper, the greater weight of more water above the water to the sides of will result in greater pressure there which will be transmitted in all directions including toward you.
Another way to look at this is if the pressure were less under the object, the greater pressure on the sides would "push" more against this lower pressure region until the pressures were equal.
Best Answer
We'll assume all the rooms and other containers are airtight, and that temperature is constant, for sake of simplicity.
If you put a mass of air in a bottle and seal it, it exerts pressure on the inside of the bottle. The pressure is dependent only on the amount of air, the volume of the bottle and the temperature. Since the bottle is rigid the volume does not change, and we're assuming constant temperature, so there's really no difference between that bottle of air in space than at sea level. The pressure inside is the same.
The same goes for a closed room. The air pressure on your body doesn't change when you close the door, because the air inside the room is the same amount at the same volume and temperature as before. At this point you could use a ridiculously large crane to lift the whole room into space and you still wouldn't boil away, because you're in a sealed room and the air pressure stays the same around you as you go from the ground into space. The air pressure outside the room changes, but luckily your concrete room is inelastic, so it "holds in" the pressure.