**1. What is elastic behavior in solids?**

**Answer:** Elastic behavior in solids refers to the property of a material to return to its original shape and size after the removal of an applied force.

**2. Describe the stress-strain relationship.**

**Answer:** The stress-strain relationship describes how a material deforms under stress, with stress being the force applied per unit area and strain being the deformation produced. It typically shows a linear relationship within the elastic limit.

**3. State Hooke’s Law.**

**Answer:** Hooke’s Law states that, within the elastic limit, the strain in a material is directly proportional to the applied stress. Mathematically, it is expressed as

where **σ** is stress, **ϵ** is strain, and **E** is Young’s modulus.

**4. What is Young’s modulus?**

**Answer:** Young’s modulus is a measure of the stiffness of a solid material. It is defined as the ratio of tensile stress to tensile strain.

**5. Define bulk modulus.**

**Answer:** The bulk modulus is a measure of a material’s resistance to uniform compression. It is defined as the ratio of an infinitesimal pressure increase to the resulting relative decrease in volume.

**6. Explain the modulus of rigidity.**

**Answer:** The modulus of rigidity, also known as shear modulus, is a measure of a material’s ability to withstand shear stress. It is defined as the ratio of shear stress to shear strain.

**7. What is the pressure due to a fluid column?**

**Answer:** The pressure due to a fluid column is given by the equation

where **h** is the height of the fluid column, **ρ** is the density of the fluid, and **g** is the acceleration due to gravity.

**8. State Pascal’s law and its applications.**

**Answer:** Pascal’s law states that in a confined fluid, a change in pressure is transmitted equally in all directions. Applications include hydraulic presses and brake systems.

**9. Describe the effect of gravity on fluid pressure.**

**Answer:** Gravity causes a pressure gradient in a fluid, with pressure increasing with depth due to the weight of the fluid above.

**10. What is viscosity?**

**Answer:** Viscosity is a measure of a fluid’s resistance to flow or deformation. It describes the internal friction within the fluid.

**11. State Stokes’ law.**

**Answer:** Stokes’ law states that the force of viscosity on a small sphere moving through a viscous fluid is directly proportional to the radius of the sphere, the fluid’s viscosity, and the velocity of the sphere. Mathematically,

**12. What is terminal velocity?**

**Answer:** Terminal velocity is the constant speed that a freely falling object eventually reaches when the resistance of the medium prevents further acceleration.

**13. Differentiate between streamline and turbulent flow.**

**Answer:** Streamline (laminar) flow occurs when fluid flows in parallel layers with no disruption between them, while turbulent flow is characterized by chaotic changes in pressure and flow velocity.

**14. What is critical velocity in fluid dynamics?**

**Answer:** Critical velocity is the maximum velocity at which a fluid can flow through a pipe without becoming turbulent.

**15. State Bernoulli’s principle and its applications.**

**Answer:** Bernoulli’s principle states that in a flowing fluid, an increase in velocity occurs simultaneously with a decrease in pressure or potential energy. Applications include airplane wings, Venturi meters, and carburetors.

**16. What is surface energy and surface tension?**

**Answer:** Surface energy is the energy required to increase the surface area of a liquid due to intermolecular forces. Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible.

**17. Define angle of contact.**

**Answer:** The angle of contact is the angle formed between the tangent to the liquid surface and the solid surface at the point of contact.

**18. Explain excess pressure across a curved surface.**

**Answer:** Excess pressure across a curved surface is the difference in pressure between the inside and outside of a curved surface, such as a bubble or drop. It is given by

for a drop or bubble of radius **r**, where **γ** is the surface tension.

**19. Describe the application of surface tension in drops, bubbles, and capillary rise.**

**Answer:** Surface tension causes droplets to form spherical shapes, bubbles to have a spherical outer layer, and allows liquids to rise or fall in capillary tubes depending on the adhesive and cohesive forces.

**20. What are the modes of heat transfer?**

**Answer:** The modes of heat transfer are conduction (transfer through a solid material), convection (transfer through fluid motion), and radiation (transfer through electromagnetic waves).

**21. Explain thermal expansion and its types.**

**Answer:** Thermal expansion is the increase in the size of a material as its temperature increases. The types are linear expansion (change in one dimension), area expansion (change in two dimensions), and volumetric expansion (change in three dimensions).

**22. Define specific heat capacity.**

**Answer:** Specific heat capacity is the amount of heat required to raise the temperature of one kilogram of a substance by one degree Celsius.

**23. What is calorimetry?**

**Answer:** Calorimetry is the measurement of the amount of heat released or absorbed during a chemical reaction, physical change, or heat capacity measurement.

**24. Explain the concept of latent heat.**

**Answer:** Latent heat is the heat required to change the state of a substance without changing its temperature. It includes latent heat of fusion (solid to liquid) and latent heat of vaporization (liquid to gas).

**25. Describe conduction in heat transfer.**

**Answer:** Conduction is the transfer of heat through a material without the movement of the material itself, typically occurring in solids through lattice vibrations and free electron movement.

**26. What is convection in heat transfer?**

**Answer:** Convection is the transfer of heat by the physical movement of a fluid (liquid or gas) caused by temperature differences within the fluid.

**27. Explain radiation in heat transfer.**

**Answer:** Radiation is the transfer of heat through electromagnetic waves without the need for a medium. It can occur in a vacuum, such as the heat from the sun reaching the earth.

**28. What is terminal velocity and how is it determined?**

**Answer:** Terminal velocity is the steady speed achieved by an object freely falling through a fluid when the forces of gravity and drag are equal and opposite. It is determined by factors like the object’s size, shape, and the fluid’s viscosity.

**29. What are streamline and turbulent flows?**

**Answer:** Streamline flow is smooth and orderly, where fluid particles move in parallel layers. Turbulent flow is chaotic, with fluid particles moving in irregular paths, leading to eddies and vortices.

**30. Discuss the applications of Bernoulli’s principle.**

**Answer:** Applications of Bernoulli’s principle include aircraft wing design for lift, carburetors in engines, and Venturi meters for measuring fluid flow rates.