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 .