Surface Tension and Liquid Behavior Quiz

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Questions and Answers

What happens to the surface tension of a liquid as the temperature increases?

It increases.

It decreases. (correct)

It fluctuates unpredictably.

It remains constant.

What is the effect of contamination on the surface tension of a liquid?

Contamination has no effect on surface tension.

Contamination can either increase or decrease surface tension depending on the type of contaminant.

Contamination always decreases surface tension. (correct)

Contamination always increases surface tension.

What shape does a liquid take when it is weightless?

A cube.

An irregular shape.

A flat sheet.

A sphere. (correct)

What is the angle of contact between pure water and glass?

0 degrees (B) Signup and view all the answers

What is the critical temperature of a liquid?

The temperature at which the liquid boils. (D) Signup and view all the answers

What effect do wetting agents have on the angle of contact between a liquid and a solid surface?

Wetting agents decrease the angle of contact. (D) Signup and view all the answers

What is the relationship between the angle of contact and temperature?

Angle of contact is inversely proportional to temperature. (D) Signup and view all the answers

What is the effect of surface tension on the shape of a liquid drop?

Surface tension causes liquid drops to be spherical. (B) Signup and view all the answers

What are the two main forces acting on a liquid droplet?

Gravitational force and force of surface tension (A) Signup and view all the answers

Which force is more dominant for smaller liquid droplets?

Force of surface tension (D) Signup and view all the answers

Which of the following statements is TRUE about the relationship between the angle of contact and capillary action?

A liquid with an angle of contact less than 90° will show capillary rise. (A) Signup and view all the answers

Which of the following factors DOES NOT affect the flow of a liquid through porous media?

The density of the liquid (A) Signup and view all the answers

Consider a liquid contained in a vessel where adhesive forces are weak compared to cohesive forces. What will be the shape of the liquid surface near the solid?

Convex (C) Signup and view all the answers

Why does mercury not wet glass, wood, or iron?

Cohesive force is greater than adhesive force (A) Signup and view all the answers

Which of the following is NOT an example of capillarity in everyday life?

A spoon sinking in a bowl of water (C) Signup and view all the answers

How does ploughing fields help preserve moisture in the soil?

It breaks up the soil crust, reducing evaporation (C) Signup and view all the answers

What effect does ploughing have on soil porosity?

It increases porosity, allowing water and air circulation. (D) Signup and view all the answers

How does ploughing improve soil structure?

By breaking up clods to create a crumbly structure. (C) Signup and view all the answers

Why is it important for soil to hold onto moisture?

To promote healthy plant growth and maintain soil health. (C) Signup and view all the answers

In the ascent formula, what represents the liquid's density?

d (C) Signup and view all the answers

What does the term 'capillary rise' refer to in the context of the ascent formula?

The height to which a liquid can rise in a cylindrical tube. (C) Signup and view all the answers

What does the coefficient of viscosity represent?

The tangential force needed to maintain a unit velocity gradient. (A) Signup and view all the answers

How does viscosity change with temperature for liquids?

Viscosity decreases with temperature. (A) Signup and view all the answers

What is the dimensional formula of viscosity?

M^1L^{-1}T^{-1} (C) Signup and view all the answers

In the context of viscosity, which statement is true about gases compared to liquids?

Viscosity of gases increases with temperature. (B) Signup and view all the answers

What does shear stress relate to in a fluid?

The intensity of internal friction. (C) Signup and view all the answers

Which factor does NOT affect the viscosity of a fluid?

Color of the fluid. (D) Signup and view all the answers

When measuring the rate of shear strain, what is typically measured over time?

The velocity of the fluid. (D) Signup and view all the answers

For a fluid with a unit area of parallel layers, what defines the strain rate?

The tangential force applied. (B) Signup and view all the answers

What effect does decreasing the area of the cross section of a pipe have on the velocity of water?

It increases the velocity. (B) Signup and view all the answers

Which of the following best describes Poiseuille’s law?

Volume flow rate is proportional to the pressure difference and the radius to the power of four. (D) Signup and view all the answers

If Pema wants to increase the speed of water flowing from a pipe, what should she do?

Press the mouth of the pipe with her thumb. (C) Signup and view all the answers

What is the relationship between the pressure and the volume flow rate in a pipe according to Poiseuille's law?

Higher pressure results in higher volume flow rate. (C) Signup and view all the answers

What does the term 'Q' represent in the context of Poiseuille’s law?

The volume flow rate of the fluid. (C) Signup and view all the answers

What is the formula used to calculate the height of liquid raised in a capillary tube?

$P_i - P_o = hdg$ (D) Signup and view all the answers

What is the significance of radius 'R' in Poiseuille’s law?

Flow rate is proportional to the fourth power of the radius. (A) Signup and view all the answers

In the scenario of a capillary tube on an artificial satellite, how does the rise of water compare to an Earth experiment?

It would not rise at all. (C) Signup and view all the answers

In Pema's observation, what happens to the distance the water can travel when she presses the pipe's mouth?

The distance can increase. (D) Signup and view all the answers

Which factor is NOT considered in determining volume flow rate according to Poiseuille’s law?

Temperature of the fluid. (B) Signup and view all the answers

What is the primary characteristic of laminar flow?

It occurs at low velocities. (C) Signup and view all the answers

Which of the following best describes turbulent flow?

A chaotic and disordered motion of particles. (C) Signup and view all the answers

What is the effect of surface tension on the height of liquid in a capillary tube?

It increases the height of liquid raised. (A) Signup and view all the answers

How is the rise of sap in a capillary tube related to its radius?

Inversely proportional to the radius. (D) Signup and view all the answers

What factors must be considered when calculating the radius of a capillary tube that raises sap?

Density, contact angle, and surface tension. (B) Signup and view all the answers

If water rises to 0.1m in a capillary tube on Earth, what happens to this behavior in space?

It will not be able to rise at all. (A) Signup and view all the answers

Study Notes

Chapter 2: Force & Motion in Fluids (7%)

Fluids adapt to container boundaries, unlike solids. They flow when external force is applied.
Examples include water, honey, water vapor, and oxygen.
Acceleration due to gravity (g) is calculated using Newton's law of gravitation.
The acceleration 'g' is independent of the body's mass.
Acceleration 'g' also remains relatively constant near the earth's surface.
Acceleration due to gravity varies with altitude. It decreases as the distance from the Earth's surface increases.
At sea level, 'g' is approximately 9.81m/s².
For Earth, G ≈ 6.67 x 10⁻¹¹ Nm²/kg², R ≈ 6.38 x 10⁶ m, Me ≈ 5.98 x 10²⁴ kg.
For Moon, G ≈ 6.67 x 10⁻¹¹ Nm²/kg², R ≈ 1.74 x 10⁶ m, Mm ≈ 7.35 x 10²² kg.
The body's mass remains the same regardless of location, but weight differs due to 'g' variations.
On the Moon, a 1kg object weighs about 1.67 N compared to 9.8N on Earth.

Motion of a Body Falling in Uniform Gravitational Field with Fluid (Air) Resistance

A falling body experiences gravitational and resisting forces in opposite directions.
Terminal velocity is the maximum constant velocity reached when resisting force equals the weight.
Terminal velocity (vt) is calculated using the equation vt = mg/k, where k is a constant.
Velocity increases exponentially initially and approaches a constant value (terminal velocity).
Acceleration decreases exponentially with time. As the body reaches terminal velocity, acceleration becomes zero.

Surface Tension

Surface tension (s) is a property of a liquid's free surface. It tends to minimize surface area.
The surface acts like a stretched membrane due to cohesive forces within the liquid.
Spheres have the least surface area for a given volume.
Surface tension is force per unit length perpendicular to an imaginary line on the liquid's surface (SI unit: N/m).
Surface tension decreases with increasing temperature.
Highly soluble substances increase surface tension, while sparingly soluble ones decrease it.
- Examples of surface tension applications include: droplet formation, soap bubbles, insects walking on water.
Molecular theory of surface tension: Surface molecules are pulled inward by cohesive forces.
Surface molecules have higher potential energy than molecules inside the liquid.

Molecular Theory for Surface Tension

Molecules at the surface experience a net downward force to the interior.
Moving a molecule from the interior to the surface requires work (increase in potential energy).
Liquid surfaces tend to have minimum surface area.

Surface Film

Surface film is a thin layer of liquid near the surface, with a thickness equal to the molecular range of the liquid.
Molecules in this film experience an inward cohesive force.

Factors Affecting Surface Tension

Surface tension is inversely proportional to temperature.
Highly soluble substances increase surface tension, while sparingly-soluble substances decrease it.
Examples include detergent effects, which reduce surface tension, thereby improving cloth cleaning efficiency.

Applications of Surface Tension

Washing cloths with soap
Adding flux in soldering
Spreading of antiseptics
Floating of objects like ducks on water.

Relation between Surface Tension and Surface Energy

Surface energy is potential energy per unit area of a liquid's surface.
The work required to increase a liquid's surface area is stored as surface energy.
Surface energy is equal to surface tension: T = W/ΔA

Rotation Between Liquid Tension and Surface Energy

Liquid films have two free surfaces, so work done is double the surface tension times the change in area (2TΔA).
Surface energy and surface tension relate as T = W/ΔA.

Types of Fluid Flow

Streamline flow: All particles follow the same path and have same velocity at a given point.
Tube of flow: Streamlines enclosed by a tube through which a fluid moves.

Laminar Flow

A continuous flow in parallel layers. Adjacent layers do not mix. Ideal condition for a uniform flow pattern. Velocity is constant.

Turbulent Flow

Disordered flow with mixing of layers. High speeds and irregularities. Velocity is not constant.

Critical Velocity

Velocity beyond which fluid flow becomes turbulent.

Viscosity of Fluids

Resistance to flow due to friction between adjacent layers.
Affected by temperature and fluid nature (liquids are more viscous than gases).
Laminar flow is ideal for low velocities and high viscosity.
Turbulent flow results from high speeds and low viscosity. (Low viscosity means more mixing.)

Reynolds Number

A dimensionless quantity that predicts the flow pattern (laminar or turbulent).

Bernoulli's Principle

In a steady streamline flow of an ideal fluid, the total energy (pressure + kinetic + potential) per unit mass remains constant throughout the liquid.
Relationship: P₁ + ½ρv₁² + ρgh₁ = P₂ + ½ρv₂² + ρgh₂

Capillarity

The rise or fall of a liquid in a narrow tube (capillary).
Depends on the liquid's surface tension, contact angle, and the tube's radius.

Equation of Continuity

For incompressible fluids: A₁v₁ = A₂v₂ (A= area, v = velocity)
Volume flow rate is constant.

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Description

Test your knowledge on the effects of temperature and contamination on surface tension, the shape of liquids in various conditions, and the dynamics of liquid droplets. This quiz covers principles of physics related to liquid behavior and properties.