Viscosity
Q. A fluid with a viscosity of 0.1 Pa·s flows through a pipe of radius 0.05 m. If the pressure difference across the pipe is 1000 Pa, what is the flow rate?
A.
0.01 m³/s
B.
0.02 m³/s
C.
0.03 m³/s
D.
0.04 m³/s
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Solution
Using Poiseuille's law, the flow rate Q = (π * r^4 * ΔP) / (8 * η * L). Assuming L = 1 m, Q = (π * (0.05)^4 * 1000) / (8 * 0.1 * 1) = 0.01 m³/s.
Correct Answer: A — 0.01 m³/s
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Q. A fluid with a viscosity of 0.1 Pa·s flows through a pipe of radius 0.05 m. What is the shear stress if the flow velocity is 1 m/s?
A.
0.1 Pa
B.
0.2 Pa
C.
0.4 Pa
D.
0.5 Pa
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Solution
Shear stress = viscosity × (velocity/radius) = 0.1 × (1/0.05) = 2 Pa.
Correct Answer: B — 0.2 Pa
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Q. A fluid with a viscosity of 0.1 Pa·s flows through a pipe of radius 0.05 m. What is the shear stress if the flow rate is 0.01 m³/s?
A.
0.4 Pa
B.
0.2 Pa
C.
0.1 Pa
D.
0.5 Pa
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Solution
Using the formula for shear stress, τ = (4 * η * Q) / (π * r^3), we find τ = 0.4 Pa.
Correct Answer: A — 0.4 Pa
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Q. If a fluid has a viscosity of 0.5 Pa·s, what does this indicate about its flow characteristics?
A.
It flows easily
B.
It is very thick
C.
It is a gas
D.
It is a low-density fluid
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Solution
A viscosity of 0.5 Pa·s indicates that the fluid is relatively thick and flows less easily compared to fluids with lower viscosity.
Correct Answer: B — It is very thick
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Q. If the temperature of a liquid increases, what happens to its viscosity?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Varies unpredictably
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Solution
The viscosity of a liquid generally decreases with an increase in temperature.
Correct Answer: B — Decreases
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Q. If the viscosity of a fluid is doubled, what happens to the flow rate through a pipe, assuming all other factors remain constant?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases fourfold
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Solution
If viscosity is doubled, the flow rate through a pipe will halve, as flow rate is inversely proportional to viscosity.
Correct Answer: B — Halves
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Q. If the viscosity of a fluid is doubled, what happens to the flow rate through a constant diameter pipe?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases fourfold
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Solution
If viscosity is doubled, the flow rate through a constant diameter pipe is halved.
Correct Answer: B — Halves
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Q. If the viscosity of a fluid is high, what does it imply about the fluid's flow?
A.
It flows easily
B.
It flows slowly
C.
It is incompressible
D.
It is a gas
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Solution
A high viscosity indicates that the fluid flows slowly.
Correct Answer: B — It flows slowly
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Q. If the viscosity of a liquid is doubled, how does it affect the flow rate through a pipe?
A.
Flow rate doubles
B.
Flow rate halves
C.
Flow rate remains the same
D.
Flow rate quadruples
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Solution
According to Poiseuille's law, if viscosity is doubled, the flow rate is halved, assuming all other factors remain constant.
Correct Answer: B — Flow rate halves
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Q. If the viscosity of a liquid is doubled, what happens to the flow rate through a pipe, assuming all other factors remain constant?
A.
Flow rate doubles
B.
Flow rate halves
C.
Flow rate remains the same
D.
Flow rate quadruples
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Solution
According to Poiseuille's law, if viscosity is doubled, the flow rate will be halved, assuming other factors remain constant.
Correct Answer: B — Flow rate halves
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Q. In a capillary tube, how does the viscosity of a fluid affect the height to which it rises?
A.
Higher viscosity leads to higher rise
B.
Higher viscosity leads to lower rise
C.
Viscosity has no effect
D.
It depends on the tube diameter
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Solution
Higher viscosity results in a lower height of rise in a capillary tube due to greater resistance to flow.
Correct Answer: B — Higher viscosity leads to lower rise
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Q. In a fluid flowing through a pipe, what effect does increasing the temperature have on its viscosity?
A.
Increases viscosity
B.
Decreases viscosity
C.
No effect
D.
Depends on the fluid
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Solution
Increasing the temperature generally decreases the viscosity of a fluid, making it flow more easily.
Correct Answer: B — Decreases viscosity
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Q. In a fluid flowing through a pipe, which factor does NOT affect the viscosity?
A.
Temperature
B.
Pressure
C.
Fluid density
D.
Fluid composition
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Solution
While temperature, pressure, and fluid composition affect viscosity, fluid density does not directly affect viscosity.
Correct Answer: C — Fluid density
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Q. In a viscometer, what does the time taken for a fluid to flow through a capillary tube indicate?
A.
Density of the fluid
B.
Viscosity of the fluid
C.
Temperature of the fluid
D.
Pressure of the fluid
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Solution
The time taken for a fluid to flow through a capillary tube is directly related to its viscosity.
Correct Answer: B — Viscosity of the fluid
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Q. In which of the following scenarios does viscosity increase?
A.
Heating a fluid
B.
Cooling a fluid
C.
Adding a solvent
D.
Increasing pressure
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Solution
Viscosity generally increases when a fluid is cooled.
Correct Answer: B — Cooling a fluid
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Q. In which of the following scenarios would you expect a fluid to have lower viscosity?
A.
At lower temperatures
B.
At higher temperatures
C.
Under high pressure
D.
In a narrow pipe
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Solution
Fluids generally have lower viscosity at higher temperatures.
Correct Answer: B — At higher temperatures
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Q. In which of the following scenarios would you expect a fluid to have the lowest viscosity?
A.
High temperature
B.
Low temperature
C.
High pressure
D.
Low pressure
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Solution
A fluid typically has the lowest viscosity at high temperatures.
Correct Answer: A — High temperature
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Q. In which of the following scenarios would you expect to observe a decrease in viscosity?
A.
Cooling a liquid
B.
Heating a liquid
C.
Increasing pressure
D.
Adding a solute
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Solution
Heating a liquid generally decreases its viscosity, allowing it to flow more freely.
Correct Answer: B — Heating a liquid
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Q. In which of the following scenarios would you expect to see the effects of viscosity most prominently?
A.
A river flowing rapidly
B.
Oil pouring from a bottle
C.
Air moving around a plane
D.
Water boiling
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Solution
The effects of viscosity are most prominently observed when oil pours from a bottle, as it flows slowly due to its higher viscosity.
Correct Answer: B — Oil pouring from a bottle
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Q. What effect does adding salt to water have on its viscosity?
A.
Increases viscosity
B.
Decreases viscosity
C.
No effect
D.
Varies with concentration
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Solution
Adding salt to water generally increases its viscosity.
Correct Answer: A — Increases viscosity
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Q. What happens to the viscosity of a gas as temperature increases?
A.
Viscosity decreases
B.
Viscosity increases
C.
Viscosity remains constant
D.
Viscosity fluctuates
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Solution
For gases, viscosity increases with an increase in temperature due to increased molecular activity and collisions.
Correct Answer: B — Viscosity increases
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Q. What happens to the viscosity of a liquid as temperature increases?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Varies unpredictably
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Solution
As temperature increases, the viscosity of a liquid generally decreases because the increased thermal energy allows the molecules to move more freely.
Correct Answer: B — Decreases
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Q. What happens to the viscosity of gases with an increase in temperature?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Varies randomly
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Solution
The viscosity of gases increases with an increase in temperature due to increased molecular motion.
Correct Answer: A — Increases
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Q. What is the effect of adding a solute to a solvent on the viscosity of the solution?
A.
Increases viscosity
B.
Decreases viscosity
C.
No effect
D.
Depends on the solute
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Solution
Adding a solute to a solvent typically increases the viscosity of the solution due to the interactions between solute and solvent molecules.
Correct Answer: A — Increases viscosity
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Q. What is the effect of adding salt to water on its viscosity?
A.
Increases viscosity
B.
Decreases viscosity
C.
No effect
D.
Depends on temperature
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Solution
Adding salt to water generally increases its viscosity.
Correct Answer: A — Increases viscosity
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Q. What is the effect of increasing the molecular weight of a polymer on its viscosity?
A.
Viscosity decreases
B.
Viscosity increases
C.
Viscosity remains the same
D.
Viscosity becomes unpredictable
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Solution
Increasing the molecular weight of a polymer generally leads to an increase in viscosity due to longer chain lengths and entanglements.
Correct Answer: B — Viscosity increases
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Q. What is the effect of pressure on the viscosity of gases?
A.
Increases viscosity
B.
Decreases viscosity
C.
No effect
D.
Depends on temperature
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Solution
The viscosity of gases increases with an increase in pressure.
Correct Answer: A — Increases viscosity
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Q. What is the effect of pressure on the viscosity of liquids?
A.
Increases viscosity
B.
Decreases viscosity
C.
No effect
D.
Depends on the temperature
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Solution
For most liquids, increasing pressure tends to increase viscosity, although the effect is generally small.
Correct Answer: A — Increases viscosity
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Q. What is the effect of temperature on the viscosity of liquids?
A.
Increases with temperature
B.
Decreases with temperature
C.
Remains constant
D.
Varies randomly
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Solution
For most liquids, viscosity decreases with an increase in temperature due to increased molecular motion.
Correct Answer: B — Decreases with temperature
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Q. What is the primary cause of viscosity in fluids?
A.
Molecular interactions
B.
Temperature
C.
Pressure
D.
Density
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Solution
Viscosity arises primarily from molecular interactions within the fluid, which resist flow.
Correct Answer: A — Molecular interactions
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