Properties of Matter:

• Due to surface tension, the free surface of a liquid behaves like a stretched elastic membrane tending to contract so as to have minimum surface area. It is measured as the force per unit length perpendicular to an imaginary line on the liquid surface.
• Pressure is defined as the ratio of the force to the area on which it acts. That is : P = F /A

The fluid pressure at a point within a fluid is given as :

P = h ρ g

• According to the Pascal's law, pressure applied at any point on the surface of a given mass of an enclosed liquid at rest is transmitted over the whole liquid.
• Archimedes' principle states in which there is an apparent loss in the weight of a body immersed in a liquid (or gas) and this loss of weight is equal to the weight of the liquid (or gas) displaced by it.
• An ideal fluid is incompressible and its flow is laminar, non-viscous and irrotational. A flow of liquid is of two types. Those are given below:

(i) Streamline motion, and

(ii) Turbulent motion.

• An equation of continuity is a consequence of the principle of conservation of mass of liquid and for streamline flow of a liquid is

a₁ v₁ = a₂ v₂

where a₁ and a₂ are the areas of two different cross-sections of a tube of flow and v₁ and v₂ respectively are the velocities of flow through these sections.

• The Bernoulli's equation is an expression representing the principle of conservation of energy for liquids. It is expressed as:

P/ ρ + gh + v²/2= constant

• The property by virtue of which a liquid opposes relative motion between its different layers is called viscosity. It is similar to the frictional force experienced by solids in motion.
• The property of matter to regain its natural shape and size or to oppose any attempt to deform it is called elasticity.
• The internal restoring force, arising due to an external deforming force applied on a body, and acting per unit area of cross-section of the body is called stress. The stress may be longitudinal, compressional and shearing.
• Strain is defined as the change in dimension of a body per unit dimension.

Strains are of three types, namely

(i) Linear strain,

(ii) Volume strain, and

(iii) Shearing strain.

• Hooke's law states that, within elastic limit, the stress is directly proportional to the corresponding strain.