Viscosity
✅
Viscosity- The property of liquid by virtue of which it opposes the relative
motion of its different layers.
It is similar to solid friction because it acts tangentially backwards and
opposes relative motion and occurs due to intermolecular force. It is
dissimilar to solid friction because it depends on velocity, area of contact
while solid friction does not. viscosity does not depend on normal reaction
but solid friction does.
✅
Newton’s Law- viscous force is directly proportional to area of contact
and velocity gradient. F =- nAdv/dx ; Where n is the proportionality constant
known as coefficient of viscosity. Negative sign indicates its an opposing
force.
✅
Coefficient of Viscosity- Its SI unit is decapoise or N.s/m^2 or kg
m^-1s^-1
Its CGS unit is poise or dyn.s/cm^2 or g cm^-1s^-1
n=-F when A=1 and dv/dx = 1
thus it is defined as the tangential backward viscous force acting on a unit
area with unit velocity gradient.
✅
Stoke’s Law- 6πηrvt
When a solid body moves through a viscous medium a layer of liquid in
contact with the solid surface is in rest and moves along with the body. The
other layers oppose this movement. The viscous force increases with the
increase in velocity. We assume that the viscous force F is
Fαηⁿ
Fαrⁿ
Fαvⁿ
Solve dimensionally
Fαηⁿrⁿvⁿ
F=kηⁿrⁿvⁿ
MLT²=k (ML⁻¹T⁻¹)ⁿ (L)ⁿ (LT⁻¹)ⁿ
F=6πηrvt experimentally k=6π
✅
Viscosity- The property of liquid by virtue of which it opposes the relative
motion of its different layers.
It is similar to solid friction because it acts tangentially backwards and
opposes relative motion and occurs due to intermolecular force. It is
dissimilar to solid friction because it depends on velocity, area of contact
while solid friction does not. viscosity does not depend on normal reaction
but solid friction does.
✅
Newton’s Law- viscous force is directly proportional to area of contact
and velocity gradient. F =- nAdv/dx ; Where n is the proportionality constant
known as coefficient of viscosity. Negative sign indicates its an opposing
force.
✅
Coefficient of Viscosity- Its SI unit is decapoise or N.s/m^2 or kg
m^-1s^-1
Its CGS unit is poise or dyn.s/cm^2 or g cm^-1s^-1
n=-F when A=1 and dv/dx = 1
thus it is defined as the tangential backward viscous force acting on a unit
area with unit velocity gradient.
✅
Stoke’s Law- 6πηrvt
When a solid body moves through a viscous medium a layer of liquid in
contact with the solid surface is in rest and moves along with the body. The
other layers oppose this movement. The viscous force increases with the
increase in velocity. We assume that the viscous force F is
Fαηⁿ
Fαrⁿ
Fαvⁿ
Solve dimensionally
Fαηⁿrⁿvⁿ
F=kηⁿrⁿvⁿ
MLT²=k (ML⁻¹T⁻¹)ⁿ (L)ⁿ (LT⁻¹)ⁿ
F=6πηrvt experimentally k=6π
