Definitions [10]
Define stress.
The force per unit area is called as stress.
Stress, σ = `"Force"/"Area" = "F"/"A"`
Define strain.
Strain is defined as the ratio of change in size to the original size of an object. It measures the degree of deformation.
Strain, ε = `"Change in size"/"Original size" = (Δ"L")/"L"`
Define Poisson’s ratio.
Poisson’s ratio, which is defined as the ratio of relative contraction (lateral strain) to relative expansion (longitudinal strain).
It is denoted by the symbol μ.
Poisson’s ratio, μ = `"Lateral strain"/"Longitudinal strain"`
Define the coefficient of viscosity of a liquid.
The coefficient of viscosity of a liquid is defined as the viscous force acting tangentially per unit area of a liquid layer having a unit velocity gradient in a direction perpendicular to the direction of flow of the liquid.
Define terminal velocity.
The maximum constant velocity acquired by a body while falling freely through a viscous medium is called the terminal velocity VT.
Define velocity gradient.
The rate of change of velocity (dv) with distance (dx) measured from a stationary layer is called velocity gradient.
∴ Velocity gradient = `(dv)/dx`
Define the angle of contact for a given pair of solid and liquid.
The angle between tangents drawn at the point of contact to the liquid surface and the solid surface inside the liquid is called the angle of contact for a pair of solid and liquid. It is denoted by θ.
Define the surface tension of a liquid.
Surface tension is defined as the force acting on a unit length of an imaginary line drawn on the free surface of the liquid, the direction of the force being perpendicular to the line so drawn and acting parallel to the surface.
Define angle of contact.
When a liquid is in contact with a solid, the angle between the tangent drawn to the free surface of the liquid and the surface of solid at the point of contact measured inside the liquid is called the angle of contact.
Define surface tension.
Surface tension is defined as the force per unit length acting at right angles to an imaginary line drawn on the free surface of the liquid.
