Air pressure doesn't crush everything underneath it because
A. air pressure is hypothetical and not a real force.
B. air pressure is strong enough.
C. things on earth have learned to withstand the constant pressure.
D. air pressure is exerted in all directions.
my answer is b.
The pressure is actually very immense, you have 10km of atmosphere above you. The reason this pressure does not crush us is not because it lacks the magnitude, but because our body's internal blood pressure is designed to negate its effect.
As per me, the correct answer is C
thanks !!
C was wrong
the answer was d.
However, pressure is a scalar, not a vector, so I get the feeling that the 'all directions' factor shouldn't cancel anything out, so I'm not too sure about (d).
Nevertheless, I'd like to hear one of the tutors' opinions on this.
Arora: The answer is D. In a static gas, the gas as a whole does not appear to move. The individual molecules of the gas, however, are in constant random motion. Because we are dealing with an extremely large number of molecules and because the motion of the individual molecules is random in every direction, we do not detect any motion. If we enclose the gas within a container, we detect a pressure in the gas from the molecules colliding with the walls of our container. We can put the walls of our container anywhere inside the gas, and the force per unit area (the pressure) is the same. We can shrink the size of our "container" down to a very small point (becoming less true as we approach the atomic scale), and the pressure will still have a single value at that point. Therefore, pressure is a scalar quantity, not a vector quantity. It has magnitude but no direction sense associated with it. Pressure force acts in all directions at a point inside a gas. At the surface of a gas, the pressure force acts perpendicular (at right angle) to the surface.
A closely related quantity is the stress tensor σ, which relates the vector force F via the linear relation F = σ A where F and A are vectors.
The pressure of the air pushing down on the outside is equal to the pressure of the air pushing out on the inside so there is no pressure difference and the body doesn't feel that 14.7 lbs/square inch pushing in from the outside; i.e., the outside pressure is equal to the inside pressure.
bobpursley: Yes, but I'm unable to understand how those characteristics of gases are what prevent us from being crushed by the atmosphere, rather than our internal pressure.
I advise taking a scuba diving course.
You will learn that at every depth you balance the air pressure within your lungs and body with the pressure of the water outside so that the net effect is zero. As you ascend from a depth you must remember to breathe out or there will be too much pressure inside your body, particularly the lungs. You learn to go "Ho Ho Ho" all the way up or you get what is called an "air embolism" and die.
Similarly if you ascend quickly or descend quickly in an airplane, you may need to balance the pressure inside and outside your eardrums.