NEET Study Notes for Properties of Bulk Matter: Check Definitions, Important Formulas, and Sample Questions

NEET Study Notes on Properties of Bulk Matter: Stress is defined as the internal restoring force that acts per unit area on a deformed body. Strain is the ratio of change in size and shape of the body with respect to the original shape and size of the body. In 1679, Robert Hooke gave Hooke’s law which states that within elastic limit or stress is directly proportional to strain.

• In NEET Physics Syllabus, Properties of Bulk matter include concepts like stress-strain relationship, Hooke’s law, and topics related to fluids like viscosity, surface energy, streamline and turbulent flow, etc.
• Candidates can expect around 3-4 questions from this topic in NEET 2022. With a thorough understanding of the topics, you will be able to attempt the questions in NEET Question Paper.

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NEET Study Notes on Properties of Bulk Matter: Important Topics

NEET Study Notes on Elasticity, Stress, and Strain

Elasticity

• The characteristics of a body to retain the original shape and size on the removal of the external force is called elasticity.
• A body that completely retains its original shape and size after removal of the external force is said to be perfectly elastic.

Stress

• When external forces are applied, the force per unit area that arises is known as stress. This allows us to predict elastic, plastic, and fluid behavior.

where S.I. unit is Nm^-2

Strain

The amount of change in shape and size in the original with respect to the original size and shape is called strain.

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What is a Stress-Strain Curve?

• Proportional Limit- The limit to which Hooke’s law of stress is directly proportional to strain is valid is known as the proportional limit.
• Elastic Limit- The maximum limit post which the body retains its original state after removal of the deforming force is called the elastic limit.
• Yield point- The point beyond the elastic limit when the length of wire increases without an increase in stress, is called a Yield point.
• Breaking point- Position when due to large strain, the wire breaks down is known as the breaking point. Stress is also known as breaking stress or tensile strength.

Hooke’s Law

In 1679, Robert Hooke has given the Hooke’s Law, which states that stress is directly proportional to the strain

i.e. Stress ∝ strain 

Where this constant proportionality is called modulus of electricity or coefficient of electricity

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Young’s Modulus (Y)

Consider a long bar of cross-sectional area A with length l0 which is tied at one end. When external force Fl is applied longitudinally along the bar internal forces in the bar resist distortion, the bar then attains equilibrium in which length is greater than and external force is balanced by internal forces. The bar is stressed in this position.

Young’s Modulus measures the resistance of a solid to elongation where Y is defined as the

where ΔI is change in length of the bar when Fl is applied

Shear Modulus

Shear Modulus or the modulus of rigidity which is represented by η measures the resistance to motion of the plane of a sliding solid part

There is no change in volume. However, there is a change in shape

Poisson’s Ratio

Poisson’s Ratio is Lateral strain/longitudinal strain

Theoretical value of Poissons’s ratio ranges between -1 and 0.5 whereas the practical value of Poisson’s ratio lies between 0 and 0.5

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NEET Study Notes on Viscosity

Viscosity- Internal Friction of Fluid that opposes relative motion between different layers of fluid is called viscosity.

The viscous force between layers of fluid with gradient velocity ()

Is 

where η is the coefficient of viscosity

Reynold’s Number

Reynold’s Number is represented by N which is the pure number that determines the nature of liquid flow through a pipe.

Bernoulli’s Theorem

The sum of pressure, kinetic energy, and potential energy per unit volume remain constant in the nonviscous, streamlined flow of liquids.

i.e., + gh +v2 = constant

Where p- density of fluid

h-0

then 

Applications of Bernoulli’s Theorem

• Working of the carburetor, sprayer or atomizer.
• The action of the bunsen burner, exhaust pump, etc.
• Airfoil or workings of the aircraft wing.
• Magnus effect of a spinning ball

Flow of Liquids

The flow of liquids can be of four types- streamline motion, steady-state motion, laminar motion, and turbulent motion

• Streamline motion- When liquids are in flow, the particles in a fluid that precede or succeed a fluid particle follow the same path which is called streamline. This motion in a fluid is called streamline motion.
• Turbulent motion- the velocity of a fluid that is irregular and haphazard and loses steadiness in its motion is called turbulent motion.

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Stoke’s Law

The motion of a solid is opposed by viscous force depending on velocity, shape, and size of the body. To overcome this vicious force, the energy of the body constantly decreases.

where r is the radius of the spherical body

v is the velocity

Η is the viscosity

NEET Study Notes on Surface Tension

Surface Tension is defined as the force per unit length that acts at right angles of an imaginary line’s either side that is drawn on the free surface of the liquid.

Angle of Contact

Angle between the tangent to the liquid surface and the tangent to the solid surface is at the point of contact is called the Angle of contact. The value of angle of contact of some solids and liquids are tabulated below:

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Temperature

The physical quantity that indicates the hotness or coldness of a body is called temperature. When the heat does not flow from one body to another the bodies are said to be at the same temperature or in a position of thermal equilibrium.

What is Thermal Expansion?

Linear Expansion is the increase in length with an increase in temperature.

where l₀ is the initial length

L is the final length

ΔT is the change in temperature

α is the coefficient of linear expansion

• Areal Expansion is the increase in area with the increase in temperature.
• Volume expansion is the increase in volume with the increase in temperature.

What is the anomalous behavior of the water?

Water has a negative coefficient of expansion in volume within the temperature ranging from 0 to 4 Celsius. As a result water contracts when the temperature increases from 0 Celsius to 4 celsius. At 4 Celsius, the density of water is 1000 kg m^–3. This is known as anomalous behavior of water.

Specific Heat Capacity

The amount of heat that is required to raise the temperature of the substance by 1 degree. It is represented by

Specific Heat of Gas

The value of specific heat of gas may be positive or negative and may vary between zero to infinity.

• Molar specific heat at constant volume C_v-- The amount of heat that is required to increase the temperature of 1 mole of gas through 1 celsius at constant volume.

• Molar specific heat at constant pressure - the amount of heat that is required to increase the temperature of 1 mole of gas through 1 celsius at constant pressure.

As per Mayer’s Relation C_P – C_V = R, where R is a gas constant

Gas being heated at constant pressure leads to expansion of gas due to work done as well as an increase in temperature. Hence C_P > C_V

NEET Study Notes on Heat transfer

There are three modes of heat transfer:

• Conduction- Particles of the body at high-temperature transfer heat at a lower temperature to the particles only through collision. Only through conduction, all the solids are heated. In a vacuum, conduction does not take place.

The rate of heat flow is given by

 where 

K is the thermal conductivity (proportionality constant) which helps in measuring how heat energy is quickly conducted through the substance.

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Convection

The process of heat transfer through the movement of particles from one medium to another is known as convection. This happens due to the difference in density.

Radiation

The process by which heat is transferred without any medium from one place to another is called Radiation. Light Radiation from the sun to earth reaches through Radiation Process.

• To detect the ignition temperature of gases, Davy’s safety lamp is used that is based on conduction.
• Working of Chimney that is used in kitchens as well as factories, land and sea breezes is based on the principle of convection.
• Air thermometers, bolometers, thermophiles are used for detection of Radiation.

Stefan’s Law

According to Stefan Boltzmann, the power radiated from a black body for overall wavelength is proportional to the thermodynamic temperature of fourth power T.

for a perfectly black body

where E is the energy transmitted per second from the unit surface area of a black body

T is the temperature

σ is Stefan’s Constant

σ- 5.67×10^–8 Wm^–2 K^–4.

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Newton's Law of Cooling

According to Newton’s Law of Cooling, the rate at which heat of a body is lost is directly proportional to the difference in temperature between the body and its surroundings.

where T is the temperature of the body

T₀ Is the temperature of the surroundings

and 

Where e is the emissivity of the body

A is the area of the surface of the body

σ is Stefan’s Constant

m is the mass of the body

c is the specific heat of the body

This relationship is possible when there is not much difference between the temperature of the body and temperature of the surroundings.

NEET Sample MCQs on Properties of Bulk Matter

Question: What does the stress vs strain curve depend on?

1. Percentage of stress and strain
2. Difference between stress and strain
3. Relationship between stress and strain
4. None of the above

Answer: Relationship between stress and strain

Question: On the application of force on the body, due to deformation, a restoring force develops on the body. What is this restoring force per unit area called?

1. modulus of elasticity
2. Strain
3. Shear
4. Stress

Answer: Stress

Question: What does the modulus of elasticity depend upon?

1. Strain
2. Stress
3. Applied Force
4. None of the above

Answer: None of the above

Question: What is the total modulus of elasticity?

1. Two
2. Three
3. Four
4. One

Answer: Three

Question: What does Hooke’s Law define?

1. Elastic Limit
2. Modulus of Elasticity
3. Strain
4. Stress

Answer: Modulus of Elasticity

Question: What is k in the relation stress= k×strain?

1. Factor of plasticity
2. Modulus of elasticity
3. Relative density
4. Spring constant

Answer: modulus of elasticity

Question: Why are raindrops spherical?

1. Air resistance
2. Viscosity
3. Atmospheric pressure
4. Surface tension forces

Answer: Surface tension forces

Question: What is the property of a liquid that opposes relative motion between different layers?

1. Capillarity
2. Viscosity
3. Cohesion
4. Surface tension

Answer: Viscosity

Question: What is specific volume a reciprocal of?

1. Volume
2. Mass dentistry
3. Area
4. Mass

Answer: mass density

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