7 Questions
Which statement is true about viscosity?
Viscosity is the resistance of a fluid to flow
What is rheology?
Rheology is the science of the flow and deformation of fluids and solids.
Kinematic viscosity is obtained by dividing the absolute viscosity by the __________ of the liquid.
density
Define fluidity.
Fluidity is the reciprocal of viscosity.
Match the following viscosity units with their corresponding measurement system:
Poise = cgs unit Stoke = cgs unit CentiStoke = cgs unit cps = Viscosity of liquids at 20°C
Explain Newton's law of flow.
Newton's law of flow describes how layers of liquid slide over each other when a force is applied, with velocity directly proportional to distance from the stationary layer.
What is a Newtonian fluid?
A Newtonian fluid is a fluid whose stress versus rate of shear curve is linear and passes through the origin.
Study Notes
Rheology and Viscosity
- Rheology is the study of the flow of liquids and the deformation of solids, and viscosity is an expression of the resistance of a fluid to flow.
- The importance of rheology lies in its application in various industries, such as:
- Pharmaceuticals: affecting the consistency and smoothness of medicinal and cosmetic products.
- Cosmetics: influencing the texture and feel of products.
- Food: impacting the texture and consistency of dairy products and other materials.
- Road building: affecting the flow of materials and their packing into containers.
Newtonian Systems
- A Newtonian fluid is a fluid whose stress versus rate of shear curve is linear and passes through the origin.
- The constant of proportionality is known as the viscosity.
- Examples of Newtonian fluids: water, chloroform, castor oil, and ethyl alcohol.
Newton's Law of Flow
- The law describes the relationship between the force applied to a fluid and its resulting velocity.
- The law states that the force per unit area (F'/A) required to bring about flow is proportional to the rate of shear (G).
- Mathematically, the law can be expressed as: F'/A = η * G, where η is the coefficient of viscosity.
Viscosity
- Viscosity is a measure of a fluid's resistance to flow.
- The unit of viscosity is the poise (P), which is defined as the shearing force required to produce a velocity of 1 cm/sec between two parallel planes of liquid each 1cm2 in area and separated by a distance of 1 cm.
- The cgs units for the poise are dyne.sec/cm² or g/cm.sec.
Fluidity and Kinematic Viscosity
- Fluidity is the reciprocal of viscosity: φ = 1/η.
- Kinematic viscosity is obtained by dividing the absolute viscosity by the density of the liquid at a definite temperature: Kinematic viscosity = η/ρ.
- Units of kinematic viscosity: the stoke (S) and centiStoke (cS).
A quiz for PharmD students at Horus University's Faculty of Pharmacy, covering physical pharmacy concepts as part of the PT-124 course. Test your knowledge of physical pharmacy principles and applications in pharmaceutical technology.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
