# NCERT Solutions for Class 11 Physics Chapter 9 - Mechanical Properties of Solids

In this chapter, we will study about solids and their mechanical properties. We will read about elasticity and elasticity in solids in particular. We will also read about the concepts of stress and strain in solids. The chapter also tells us about Hooke's law and the stress-strain curve. We then move to read about elastic moduli. The chapter ends by giving us details about applications of elastic behavior of metals.

• A solid body has a definite shape and size.
• An external force is needed to bring about a change in the shape of a solid body.
• The property of a solid to regain its original shape is known as elasticity.
• Substances like mud and putty that do not tend to retain their original shapes are called plastics.
• The chapter briefly explains the elastic nature of plastic.
• We also read about the concepts of stress and strain in relation to force applied to a solid body.
• Equations in the chapter also explain Hooke's law.
• A diagrammatic representation of the stress-strain curve is also explained in the chapter.
• We then move on to reading about elastic moduli, in particular the young moduli.
• We also read about the determination of Young's moduli of the material of a wire through experimentation.
• The chapter also concentrates on the Shear modulus and the Bulk modulus and their application on some common materials.
• The ratio calculated between lateral strain to the longitudinal strain in a stretched wire is called Poisson's law.
• We read about the elastic potential energy in such a wire.
• The chapter concludes by telling us about the practical applications of elastic behavior metals.