Fill in the blanks using the word(s) from the list appended with each statement: (a) Surface tension of liquids generally . . . with temperatures (increases / decreases) (b) Viscosity of gases . . . with temperature, whereas viscosity of liquids . . . with temperature (increases / decreases) (c) For solids with elastic modulus of rigidity, the shearing force is proportional to . . . , while for fluids it is proportional to . .. (shear strain / rate of shear strain) (d) For a fluid in a steady flow, the increase in flow speed at a constriction follows (conservation of mass / Bernoulli’s principle) (e) For the model of a plane in a wind tunnel, turbulence occurs at a ... speed for turbulence for an actual plane (greater / smaller)
(a)
The correct statement is, “The surface tension of a liquid decreases with the increase in the temperature”.
When the temperature of a liquid is increased, the intermolecular forces or cohesive forces between the molecules are reduced due to which the surface tension of the liquid decreases. Hence, the surface tension of a liquid decreases with the increase in the temperature.
(b)
The correct statement is, “Viscosity of gases increase with temperature whereas viscosity of liquids decrease with temperature”.
In case of gases, in accordance with the kinetic theory of gases, viscosity is proportional to the square root of the absolute temperature. Therefore, viscosity of gases increase with temperature.
In case of liquids, when the temperature is increased the intermolecular force between the molecules of the liquid is decreased due to which, the viscosity of liquid decreases.
(c)
The correct statement is, “For solids, with elastic modulus of rigidity, the shearing force is proportional to shear strain, while for fluids it is proportional to the rate of shear strain”.
In solids, with the elastic modulus of rigidity, the shear force is directly proportional to the shear strain while in fluids, the shear force is directly proportional to the shear strain rate.
(d)
The correct statement is, “For fluids in a steady flow, the increase in flow speed at a constriction follows the principle of conservation of mass”.
The principle of conservation of mass is obeyed when the flow is steady. Therefore, for a fluid in steady flow, the increase in flow speed at a constriction follows the principle of conservation of mass.
(e)
The correct statement is, “Compared to the model of a plane in a wind tunnel, turbulence occurs at a greater speed for an actual plane”.
The turbulence depends upon Reynolds’ number, which is different for a model plane and an actual plane. The Reynolds’s number for a model plane is greater than that of an actual plane. Therefore, compared to the model of a plane in a wind tunnel, turbulence occurs at a greater speed for an actual plane.
(a)
The correct statement is, “The surface tension of a liquid decreases with the increase in the temperature”.
When the temperature of a liquid is increased, the intermolecular forces or cohesive forces between the molecules are reduced due to which the surface tension of the liquid decreases. Hence, the surface tension of a liquid decreases with the increase in the temperature.
(b)
The correct statement is, “Viscosity of gases increase with temperature whereas viscosity of liquids decrease with temperature”.
In case of gases, in accordance with the kinetic theory of gases, viscosity is proportional to the square root of the absolute temperature. Therefore, viscosity of gases increase with temperature.
In case of liquids, when the temperature is increased the intermolecular force between the molecules of the liquid is decreased due to which, the viscosity of liquid decreases.
(c)
The correct statement is, “For solids, with elastic modulus of rigidity, the shearing force is proportional to shear strain, while for fluids it is proportional to the rate of shear strain”.
In solids, with the elastic modulus of rigidity, the shear force is directly proportional to the shear strain while in fluids, the shear force is directly proportional to the shear strain rate.
(d)
The correct statement is, “For fluids in a steady flow, the increase in flow speed at a constriction follows the principle of conservation of mass”.
The principle of conservation of mass is obeyed when the flow is steady. Therefore, for a fluid in steady flow, the increase in flow speed at a constriction follows the principle of conservation of mass.
(e)
The correct statement is, “Compared to the model of a plane in a wind tunnel, turbulence occurs at a greater speed for an actual plane”.
The turbulence depends upon Reynolds’ number, which is different for a model plane and an actual plane. The Reynolds’s number for a model plane is greater than that of an actual plane. Therefore, compared to the model of a plane in a wind tunnel, turbulence occurs at a greater speed for an actual plane.
