VISCOSITY

The property of fluids by virtue of which a backward dragging force or a viscous drag acts tangentially on the layers of the fluids in motions and it tries to destroy the motion of liquid is known as viscosity .
                   

                                            
      The viscosity of liquid decreases with increase in temperature and vice versa . 
             FLOW LINE:The path of an individual particle in a moving fluid is called a flow line.
          STEADY FLOW:If the overall flow of pattern does not change with time,the flow of liquid is called steady flow.

                                  

              

                                  STREAMLINE AND TURBULENT FLOW :

The flow of liquid is said to be a streamline flow if  each particle of liquid follows exactly the same path and the same velocity as its predecessor . A streamline may be defined as a curve, the tangent to which at any point gives the direction of flow of the liquid at that point
       This holds good,however,only so long as the velocity of the liquid does not exceed a particular limiting value,called its critical velocity,beyond which the flow of the liquid loses all its steadiness and becomes zigzag,acquiring what is called a turbulent motion .


                             
                                                                          
                                   

                                                  

What is physics?

Physics is the study of nature and its law.
To understand nature is physics , and mathematics is the deluxe coach to take us there comfortably.

SURFACE TENSION

The property of  liquid  by virtue of which it behaves like a stretched elastic membrane with natural tendency to contract ( occupy ) minimum surface area . Thus a liquid surface is always in a state of tension . 
      It is also defined as the force per unit length acting tangentially and right angle on either side of an imaginary line drawn at the liquid surface .
                                       ST=F/L

UNIT     N/m 

example : 

The shape of the liquid drop is determined by the potential energy due to surface tension . For any given volume of liquid , minimum area is occupied by the sphere . When the area of the surface is minimum the potential energy is minimum due to surface tension . Hence the liquid drop is spherical in shape.

example :

Hot water is a better cleaning agent because the lower surface tension makes it a better "wetting agent" to get into pores and fissures rather than bridging them with surface tension. Soaps and detergents further lower the surface tension.

 EFFECT OF TEMPERATURE :

The surface tension of water is 72 dynes/cm at 25°C . It would take a force of 72 dynes to break a surface film of water 1 cm long. The surface tension of water decreases significantly with increase in temperature as shown in the graph. 

Hot soup is more tasteful than cold one.

The surface tension of hot soup is less than that of cold one and therefore hot soup covers more area of  the tongue.He nce hot soup is more tasty than the cold one

EINSTEIN