Revision: Fluids Science SSLC (English Medium) Class 9 Tamil Nadu Board of Secondary Education

The force which produces compression is called thrust. Its S.I unit is the newton.

A low-pressure area is an area in the atmosphere where the pressure is lower than its surrounding areas. In this situation, the wind from the surroundings blows towards the center of low pressure.

The pressure exerted by this mercury column is considered as the pressure of magnitude ‘one atmosphere’ (1 atm).

High pressure is an area of the atmosphere where the barometric pressure is higher than its surrounding areas. In this case, the wind from the center of high pressure blows towards the surrounding low-pressure areas.

SI unit of pressure is the pascal (Pa) or Nm⁻²
One Pascal: When a force of one newton acts normally on an area of one square metre (1 m²) then the pressure acting on the surface acting on the surface is called one Pascal.

RELATIVE DENSITY: “is the ratio of the density of a substance to the density of water at 4° C.”
Or
RELATIVE DENSITY “is the ratio of the mass of the substance to the mass of an equal volume of water at 4° C.”

Density of a substance is defined as “Mass per Unit volume”.

Density [d]=`"mass  of the substance"/"volume of the substance"`

d=`m/v`

UNIT OF RELATIVE DENSITY: No units since it is a pure ratio.