NCERT

According to the NCERT Solutions for Class 11 Physics Chapter 8 Mechanical Properties of Solids, when an external force is applied to a solid, the solid undergoes changes in shape or size which is called deformation. The solid deformation can be classified into:

Elastic Deformation: It is when the body returns to its original size and shape after the force is removed. It occurs within the elastic limit and follows Hooke's law. The most common examples include stretching a helical spring or a rubber band.

Plastic Deformation: It occurs beyond the elastic limit and here after the removal of the force, the body does not return to its original shape and size. Hence, the force applied leads to the permanent deformation of the solid. Common examples include deformation in putty, clay or bending of a metal wire beyond a certain limit.

The plastic deformation is irreversible and elastic deformation is reversible. These concepts are important when studying engineering, material science, and construction.

The modulus of elasticity refers to the material's capacity to withstand or resist deformation when stress is applied. There are three types of the modulus of elasticity including:

Young's Modulus (E): It is used to measure a solid's elasticity when longitudinal stress (tensile or compressive) is applied to it. Mathematically, it is represented by the following formula;

SI Unit is N/m² (Pascal, Pa).

Bulk Modulus (K): It is used to measure the ability of the material to resist volume change when uniform pressure is applied to it. Mathematically, it is:

SI Unit is N/m² (Pa)

Shear Modulus (G) or Modulus of Rigidity: It is used when a shear force is applied to measure the resistance to shape change. Mathematically, it is represented by:

SI Unit: N/m² (Pa)

The value of each modulus varies for different materials, and it describes different types of deformation.

Students can check Class 12 Chemistry Chapter 9 Amines NCERT Solutions, which can help you know name chemical reactions crucial for CBSE Board Exams and Competitive Exams like JEE and NEET:

• Gabriel Phthalimide Synthesis – Used to prepare primary amines from phthalimide via hydrolysis.

• Hoffmann Bromamide Degradation Reaction – Converts amides to primary amines with one less carbon atom using Br? and NaOH.

• Carbylamine Reaction – A test for primary amines where they react with chloroform and KOH to form isocyanides (foul-smelling).

• Acylation and Alkylation of Amines – Involves the reaction of amines with acid chlorides or alkyl halides.

• Coupling Reaction – Aryldiazonium salts react with phenols or aromatic amines to form azo dyes.

The chapter consists of fundamental topics that are important for board exams preparation as well as for competitive tests: 

• Composition and Size of the Nucleus: Understanding protons, neutrons, and nuclear density.

• Nuclear Force: The forces that hold the nucleus together. 

• Mass-Energy Equivalence (E = mc²): Einstein's equation and its significance in nuclear reactions.

• Nuclear Binding Energy: Understanding nuclear stability and energy release. 

• Radioactivity: Concepts of alpha, beta, and gamma decay. 

• Laws of Radioactive Decay: Half-life, mean life, and decay constant derivations. 

• Nuclear Fission and Fusion: Their role in power generation and astrophysical processes.

• Applications of Nuclear Physics: Uses of radioisotopes in medicine, industry, and archaeology.

While studying the mechanical properties of solids, stress and strain are fundamental concepts.

Stress: It refers to the condition when the external force is applied to a solid body and it experiences an internal restoring force per unit area. The resisting deformation due to the internal force is called stress. The formula is:

The SI unit of stress is N/m² (Pascal, Pa).

There are three types of stress -

1. When the applied force increases the length of the body, it is called tensile stress.
2. When the applied force decreases the length of the body, it is termed as the compressive stress.
3. When the force is applied tangentially and creates deformation in shape, it is called shear stress.

Strain: It is a dimension less quantity. It refers to the relative deformation produced in a body due to applied stress. The formula is:

There are three types of strain:

1. Change in length per unit original length is called the Longitudinal Strain.
2. The change in volume per unit original volume is called the Volumetric Strain.
3. Angular deformation due to shear stress is called Shear Strain.

Hooke's Law relates stress and strain by a formula. It states that within the elastic limit, stress is directly proportional to strain:

E stands for the modulus of elasticity.

Amines are organic compounds derived from ammonia (NH3 ) by replacing hydrogen atoms with alkyl or aryl groups. They are classified as primary, secondary, or tertiary based on the number of hydrogen substitutions. Their nomenclature follows IUPAC rules, using the suffix “-amine.” There are several important topics discussed throghout the chapter 9 amines such as Preparation methods, physical properties, chemical properties and named reactions.

Amines are synthesized through methods like reduction of nitro compounds, ammonolysis, Gabriel phthalimide synthesis, and Hoffmann bromamide degradation.  In terms of physical properties, Amines exhibit hydrogen bonding, affecting their boiling points and solubility. Chemically, amines are basic in nature and undergo alkylation, acylation, and electrophilic substitution in aromatic amines. Amines are widely used in chemical industries; pharmaceuticals, dyes, and organic synthesis e.g. diazonium salts, formed from aromatic amines, are crucial in dye synthesis. Students can check NCERT Solutions of Class 12 Chemistry Amines for better preparation for boards and other competiive exam.