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Saturday, May 3, 2014

Unit II Physics NDA : Some Important Facts about Physical properties

Some Important Facts


Normal atmospheric pressure is equal to 76 cm of height of mercury in the Barometer.

If h is the barometric height for a liquid of density d, then,

hdg = 76 x 13.6 x g or h = 76 x 13.6 / d

Relative Density = Density of Body / Density of Water at 4°C

A pressure applied at any point of the fluid is equally transmitted in all the directions.
Pressure is force acting perpendicular on unit area of a surface.

Pressure (P) = Force (F) / Area (A)

Pressure is scalar quantity and its unit is N/m² or Pascal (Pa).

Density of a substance can be defined as the ratio of its mass to its volume.

Density (d) = Mass (M) / Volume (v)

The unit of density is kg / m³

If we mix equal volumes of two liquids of density d₁ and d₂, then the density of the mixture is

d = d₁ + d₂ / 2

If we mix two liquids of same mass with densities d₁ and d₂, then the density of the mixture is

d = 2d₁d₂ / d₁ + d₂
If we mix two liquids of mass m₁ and m₂ having densities d₁ and d₂, then the density of the mixture is

d = m₁ + m₂ / m₁/d₁ + m₂/d₂

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