Multiple choice questions Fluid Properties

     Any substances which capable to flow and in which shear stress will develop between layers is called fluid. Generally gas and liquid state is fluid.

     When fluid is at rest position there is no motion of any layer, due to zero motion shear stress developed will be zero and duo to shear stress zero viscosity is zero.

     When any fluid flow there is resistance between layers of fluid it means shear force. This resistance consume energy to flow. To get maximum workdone theremust be zero resistance, means zero shear force. And zero viscosity i.e.μ = 0.

     Velocity is increases with increase in depth and ratio of change in velocity to the change in depth is called as velocity gradient. In another words, if we draw graph between velocity on X-axis and depth of fluid on Y-axis graph gives a line. And slope of this line is called as velocity gradient.
     i.e. ^Δu ⁄_Δy
          Where,
               Δu - is change in velocity,
               Δy - is change in depth.

     This is Newton's law of viscosity. It state that shear stress is directly proportional to the velocity gradient.
           τ   ∝   ^Δu ⁄_Δy
          Where,
               τ - is shear stress,
                ^Δu ⁄_Δy - is velocity gradient,
               Δu - is change in velocity,
               Δy - is change in depth.