It is about 100000 N / m 2. It is equivalent to a weight of 10 tones on 1 m 2.
At sea level, atmospheric pressure is equal to 76 cm of mercury column. Then, atmospheric pressure
= hdg = 76 x 13.6 x 980 dyne / cm 2
[ The atmospheric pressure does not crush our body because the pressure of the blood flowing through our circulatory system ] balanced this pressure.]
Atmospheric pressure is also measured in torr and bar. 1 torr = 1 mm of mercury column 1 bar = l0 5 Pa Aneroid barometer is used to measure atmospheric pressure.
Buoyancy When a body is partially or fully immersed in a fluid an upward force acts on it, which is called buoyant force or simply buoyancy.
The buoyant force acts at the centre of gravity of the liquid displaced ] by the immersed part of the body and this point is called the centre buoyancy.
Archimedes’ Principle When a body is partially or fully immersed in a liquid, it loses some of its weight. and it is equal to the weight of the liquid displaced by the immersed part of the body.
If T is the observed weight of a body of density σ when it is fully immersed in a liquid of density p, then real weight of the body
w = T /( 1 – p / σ) Laws of Floatation
A body will float in a liquid, if the weight of the body is equal to the weight of the liquid displaced by the immersed part of the body.
If W is the weight of the body and w is the buoyant force, then( a) If W > w, then body will sink to the bottom of the liquid.