Fluid Mechanics Test - 13

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Molecular Perspective In water, there are two types of molecules. Some molecules are at the surface, called exterior molecules, and some molecules are inside, called interior molecules. The interior molecules are attracted to all the molecules around them. The exterior molecules are attracted to only the other surface molecules and to those below the surface. So that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. The molecules always try to maintain a lower energy state and hence the exterior molecules experience a downward force. This force is known as cohesive force. As a result they try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. Thus surface tension is created. The water molecules attract one another due to the water molecule’s polar property. The hydrogen ends, which are positive in comparison to the negative ends of the oxygen, cause water to "stick " together. This is why there is surface tension. Water has very high surface tension. It is 72.8 milli newton per meter at 20°C.

Q. The energy state of the interior molecules of a fluid is

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Molecular Perspective In water, there are two types of molecules. Some molecules are at the surface, called exterior molecules, and some molecules are inside, called interior molecules. The interior molecules are attracted to all the molecules around them. The exterior molecules are attracted to only the other surface molecules and to those below the surface. So that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. The molecules always try to maintain a lower energy state and hence the exterior molecules experience a downward force. This force is known as cohesive force. As a result they try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. Thus surface tension is created. The water molecules attract one another due to the water molecule’s polar property. The hydrogen ends, which are positive in comparison to the negative ends of the oxygen, cause water to "stick " together. This is why there is surface tension. Water has very high surface tension. It is 72.8 milli newton per meter at 20°C.

Q. The water molecules attract one another due to the water molecule’s

Attempt All sub parts from each question.

Molecular Perspective In water, there are two types of molecules. Some molecules are at the surface, called exterior molecules, and some molecules are inside, called interior molecules. The interior molecules are attracted to all the molecules around them. The exterior molecules are attracted to only the other surface molecules and to those below the surface. So that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. The molecules always try to maintain a lower energy state and hence the exterior molecules experience a downward force. This force is known as cohesive force. As a result they try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. Thus surface tension is created. The water molecules attract one another due to the water molecule’s polar property. The hydrogen ends, which are positive in comparison to the negative ends of the oxygen, cause water to "stick " together. This is why there is surface tension. Water has very high surface tension. It is 72.8 milli newton per meter at 20°C.

Q. Surface tension of water is

Attempt All sub parts from each question.

Molecular Perspective In water, there are two types of molecules. Some molecules are at the surface, called exterior molecules, and some molecules are inside, called interior molecules. The interior molecules are attracted to all the molecules around them. The exterior molecules are attracted to only the other surface molecules and to those below the surface. So that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. The molecules always try to maintain a lower energy state and hence the exterior molecules experience a downward force. This force is known as cohesive force. As a result they try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. Thus surface tension is created. The water molecules attract one another due to the water molecule’s polar property. The hydrogen ends, which are positive in comparison to the negative ends of the oxygen, cause water to "stick " together. This is why there is surface tension. Water has very high surface tension. It is 72.8 milli newton per meter at 20°C.

Q. Which one of the following is the correct molecular structure of water molecule?

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Molecular Perspective In water, there are two types of molecules. Some molecules are at the surface, called exterior molecules, and some molecules are inside, called interior molecules. The interior molecules are attracted to all the molecules around them. The exterior molecules are attracted to only the other surface molecules and to those below the surface. So that the energy state of the molecules on the interior is much lower than that of the molecules on the exterior. The molecules always try to maintain a lower energy state and hence the exterior molecules experience a downward force. This force is known as cohesive force. As a result they try to maintain a minimum surface area, thus allowing more molecules to have a lower energy state. Thus surface tension is created. The water molecules attract one another due to the water molecule’s polar property. The hydrogen ends, which are positive in comparison to the negative ends of the oxygen, cause water to "stick " together. This is why there is surface tension. Water has very high surface tension. It is 72.8 milli newton per meter at 20°C.

Q. The tendency of water to maintain .............. surface area is known as surface tension.

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Newtonian and non-Newtonian fluid: Viscosity is the physical property that characterizes the flow resistance of simple fluids. Newton’s law of viscosity defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure, and is defined as the viscosity or coefficient of viscosity. Newtonian fluids obey Newton’s law of viscosity. The viscosity is independent of the shear rate. Example: air, water, alcohol etc. Non-Newtonian fluids do not follow Newton’s law thus, their viscosity (ratio of shear stress to shear rate) is not constant and is dependent on the shear rate. Example: honey, ketchup etc. Non-Newtonian fluids can be categorized into four types based on the way a fluid’s viscosity changes in response to variations in shear rate.

• Pseudoplastic: Materials whose viscosity decreases as the shear rate increases. This type of flow behavior is sometimes called shear thinning. Example: Cake batter, agar-agar and fruit juice concentrates, nail polish etc.

• Dilatant: M aterials whose viscosity increases as the shear rate increases. This type of behavior is sometimes called shear-thickening. Example: Suspension of corn starch in water and candy compounds etc..

• Thixotropic: M aterials whose viscosity decreases when sheared at a constant rate over time. Example: Yogurt, gelatin gel, honey etc.

• Rheopectic: M aterials whose viscosity increases when sheared at a constant rate over time. Example: Printer ink, gypsum paste etc.

Q. Newton’s law of viscosity states

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Newtonian and non-Newtonian fluid: Viscosity is the physical property that characterizes the flow resistance of simple fluids. Newton’s law of viscosity defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure, and is defined as the viscosity or coefficient of viscosity. Newtonian fluids obey Newton’s law of viscosity. The viscosity is independent of the shear rate. Example: air, water, alcohol etc. Non-Newtonian fluids do not follow Newton’s law thus, their viscosity (ratio of shear stress to shear rate) is not constant and is dependent on the shear rate. Example: honey, ketchup etc. Non-Newtonian fluids can be categorized into four types based on the way a fluid’s viscosity changes in response to variations in shear rate.

• Pseudoplastic: Materials whose viscosity decreases as the shear rate increases. This type of flow behavior is sometimes called shear thinning. Example: Cake batter, agar-agar and fruit juice concentrates, nail polish etc.

• Dilatant: M aterials whose viscosity increases as the shear rate increases. This type of behavior is sometimes called shear-thickening. Example: Suspension of corn starch in water and candy compounds etc..

• Thixotropic: M aterials whose viscosity decreases when sheared at a constant rate over time. Example: Yogurt, gelatin gel, honey etc.

• Rheopectic: M aterials whose viscosity increases when sheared at a constant rate over time. Example: Printer ink, gypsum paste etc.

Q. Viscosity of pseudoplastic non-Newtonian fluid

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Newtonian and non-Newtonian fluid: Viscosity is the physical property that characterizes the flow resistance of simple fluids. Newton’s law of viscosity defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure, and is defined as the viscosity or coefficient of viscosity. Newtonian fluids obey Newton’s law of viscosity. The viscosity is independent of the shear rate. Example: air, water, alcohol etc. Non-Newtonian fluids do not follow Newton’s law thus, their viscosity (ratio of shear stress to shear rate) is not constant and is dependent on the shear rate. Example: honey, ketchup etc. Non-Newtonian fluids can be categorized into four types based on the way a fluid’s viscosity changes in response to variations in shear rate.

• Pseudoplastic: Materials whose viscosity decreases as the shear rate increases. This type of flow behavior is sometimes called shear thinning. Example: Cake batter, agar-agar and fruit juice concentrates, nail polish etc.

• Dilatant: M aterials whose viscosity increases as the shear rate increases. This type of behavior is sometimes called shear-thickening. Example: Suspension of corn starch in water and candy compounds etc..

• Thixotropic: M aterials whose viscosity decreases when sheared at a constant rate over time. Example: Yogurt, gelatin gel, honey etc.

• Rheopectic: M aterials whose viscosity increases when sheared at a constant rate over time. Example: Printer ink, gypsum paste etc.

Q. Shear-thinning fluids are also called

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Newtonian and non-Newtonian fluid: Viscosity is the physical property that characterizes the flow resistance of simple fluids. Newton’s law of viscosity defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure, and is defined as the viscosity or coefficient of viscosity. Newtonian fluids obey Newton’s law of viscosity. The viscosity is independent of the shear rate. Example: air, water, alcohol etc. Non-Newtonian fluids do not follow Newton’s law thus, their viscosity (ratio of shear stress to shear rate) is not constant and is dependent on the shear rate. Example: honey, ketchup etc. Non-Newtonian fluids can be categorized into four types based on the way a fluid’s viscosity changes in response to variations in shear rate.

• Pseudoplastic: Materials whose viscosity decreases as the shear rate increases. This type of flow behavior is sometimes called shear thinning. Example: Cake batter, agar-agar and fruit juice concentrates, nail polish etc.

• Dilatant: M aterials whose viscosity increases as the shear rate increases. This type of behavior is sometimes called shear-thickening. Example: Suspension of corn starch in water and candy compounds etc..

• Thixotropic: M aterials whose viscosity decreases when sheared at a constant rate over time. Example: Yogurt, gelatin gel, honey etc.

• Rheopectic: M aterials whose viscosity increases when sheared at a constant rate over time. Example: Printer ink, gypsum paste etc.

Q. Viscosity of thixotropic non-Newtonian fluid

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Newtonian and non-Newtonian fluid: Viscosity is the physical property that characterizes the flow resistance of simple fluids. Newton’s law of viscosity defines the relationship between the shear stress and shear rate of a fluid subjected to a mechanical stress. The ratio of shear stress to shear rate is a constant, for a given temperature and pressure, and is defined as the viscosity or coefficient of viscosity. Newtonian fluids obey Newton’s law of viscosity. The viscosity is independent of the shear rate. Example: air, water, alcohol etc. Non-Newtonian fluids do not follow Newton’s law thus, their viscosity (ratio of shear stress to shear rate) is not constant and is dependent on the shear rate. Example: honey, ketchup etc. Non-Newtonian fluids can be categorized into four types based on the way a fluid’s viscosity changes in response to variations in shear rate.

• Pseudoplastic: Materials whose viscosity decreases as the shear rate increases. This type of flow behavior is sometimes called shear thinning. Example: Cake batter, agar-agar and fruit juice concentrates, nail polish etc.

• Dilatant: M aterials whose viscosity increases as the shear rate increases. This type of behavior is sometimes called shear-thickening. Example: Suspension of corn starch in water and candy compounds etc..

• Thixotropic: M aterials whose viscosity decreases when sheared at a constant rate over time. Example: Yogurt, gelatin gel, honey etc.

• Rheopectic: M aterials whose viscosity increases when sheared at a constant rate over time. Example: Printer ink, gypsum paste etc.

Q. A fluid, whose viscosity changes with the rate of deformation or shear stain is known as