Viscosity , velocity gradient and Effect of  temperature on viscosity of liquid 

Viscosity :-  Friction among horizontal fluid layer known as viscous force this property is known as viscosity.

  • it is the resistance  flow of liquid.
velocity gradient :- 
 assumption
  • speed of water at river bed is zero.
  • change in velocity height 
  • velocity gradient = 055%
  •  uniform (velocity gradient ) = change in velocity ➗ change in height 
  • non uniform change    = dv/dy
  • this velocity  gradient is necessary for viscous fore.

Effect of  temperature on viscosity of liquid : -

  • when a liquid heated the kinematic energy of its molecules increase and the intermolecular attraction become weaker 
Hence , viscosity of liquid decrease with increase in its temperature