Fluids can flow.  Gases and liquids are fluids.  They conform to the shape of their container, and in the case of gases, diffuse evenly in that container.

Objects located in fluids (like people in the air) feel pressure due to the fluid's particles bouncing off them.  How is pressure measured and how much pressure do they feel?

Pressure is the force exerted by an object divided by the area of contact.
P=F/A, so the unit of pressure is the Newton/m2, also called the Pascal.



So if my mass is 85Kg and I am standing on a wooden block with sides each 10cm, how many Pascals are put on the floor? (neglect mass of block)
P=F/A=mg/length*width=(85Kg*9.8m/s/s)/(.1m*.1m)=83300Pa


Remember that mass=density*volume?
Well, then, P=Dvg/A

Also, volume=height*area, so P=DhAg/A, the A's cancel,
leaving us with P=Dhg



What is the pressure at the bottom of a 3m swimming pool?
(density of water=1000kg/m3)

Use P=Dhg=1000 Kg/m3*3m*9.8m/s/s=29400Pa
(NOTE: This problem does NOT take the atmosphere above the pool into acount!)