Pressure

What is pressure ?

Pressure is defined as perpendicular force exerted per unit area.
If an 8 stone (112lb) woman stands on your hand in her bare feet it probably wont hurt (unless you are a wimp or she has very small feet), if the same woman wears a pair of stilletto heels and stands on your hand it will hurt.
Why ?
Because in the heeled example the same 112lbs is exerted over a much smaller area so a greater pressure is exerted.

Mathematically

Algebraically

P = F/A

P: Pressure [N m^-2]
F: Force [N]
A: Area [m²]

Units

Pressure is measured in the SI system in pascals it has dimensions of kg m^-1 s^-2 (or N m^-2).
Alternative non-SI units are

lbf in ^-2 [psi]
lbf ft^-2
millibars [mb]
inches of mercury [in hg]

Web References

National Physics Laboratory Pressure Standards


© Copyright 2000-2009 Gary Spender