NCERT Solutions for class 11 Physics Chapter 9: Mechanical properties of solids

NCERT Solutions for Class 11 Physics Chapter 9: Mechanical Properties of Solids are provided in this article below. Mechanical properties of solids define the various characteristics of solids such as their resistance to deformation and their strength. 

Chapter 9 Mechanical Properties of Solids belongs to Unit 7 Properties of Bulk Matter. Unit 7 along with Unit 8 Thermodynamics and Unit 9 Behaviour of Perfect Gases and Kinetic Theory of Gases has a weightage of 20 marks in the Class 11 Examination. The Class 11 NCERT Solutions for Mechanical Properties of Solids discusses concepts such as Elastic behaviour of solidsHooke’s law, and the Stress-strain curve.

Download PDF: NCERT Solutions for Class 11 Physics Chapter 9


NCERT Solutions for Class 11 Physics Chapter 9

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Class 11 Physics Chapter 9 – Concepts Covered

  • Stress is the ratio of the internal force F, produced when a substance is deformed, to the area A over which the force acts. 
\(Stress = {F \over A}\)
  • Strain is the ratio of the change in shape or size to the original shape or size. It is just a number and has no dimensions.
Strain is of 3 types – Longitudinal strain, Volumetric strain, and Shear strain
  • As per Hooke’s law, the ratio of stress to the corresponding strain produced within elastic limits is a constant. This constant is known as the modulus of elasticity. 
\(F_s = -kx\)
  • For a solid, in wire or a thin rod form, Young’s modulus of elasticity is defined as the ratio of longitudinal stress to longitudinal strain within the elastic limit. 

Young's Modulus

  • Poisson’s Ratio – The ratio of change in diameter (ΔD) to the original diameter (D) is known as lateral strain. The ratio of change in length (Δl) to the original length (l) is known as longitudinal strain. The ratio of lateral strain to the longitudinal strain is called Poisson’s ratio.
\(Poisson's\ Ratio\ = {Lateral\ strain \over Longitudinal\ Strain}\)

CBSE CLASS XII Related Questions

1.

A parallel plate capacitor made of circular plates each of radius R = 6.0 cm has a capacitance C = 100 pF. The capacitor is connected to a 230 V ac supply with a (angular) frequency of 300 rad s−1.

  1. What is the rms value of the conduction current?
  2. Is the conduction current equal to the displacement current?
  3. Determine the amplitude of B at a point 3.0 cm from the axis between the plates.
A parallel plate capacitor made of circular plates

      2.

      In a parallel plate capacitor with air between the plates, each plate has an area of 6 × 10–3 m2 and the distance between the plates is 3 mm. Calculate the capacitance of the capacitor. If this capacitor is connected to a 100 V supply, what is the charge on each plate of the capacitor?

          3.
          A spherical conductor of radius 12 cm has a charge of 1.6 × 10–7C distributed uniformly on its surface. What is the electric field ?
          1. inside the sphere
          2. just outside the sphere
          3. at a point 18 cm from the centre of the sphere?

              4.
              A circular disc is rotating about its own axis at uniform angular velocity \(\omega.\) The disc is subjected to uniform angular retardation by which its angular velocity is decreased to \(\frac {\omega}{2}\) during 120 rotations. The number of rotations further made by it before coming to rest is

                • 120
                • 60
                • 40
                • 20

                5.
                A convex lens of glass is immersed in water compared to its power in air, its power in water will

                  • increase
                  • decrease
                  • not change
                  • decrease for red light increase for violet light

                  6.
                  A circular disc is rotating about its own axis. An external opposing torque 0.02 Nm is applied on the disc by which it comes rest in 5 seconds. The initial angular momentum of disc is

                    • $0.1\,kgm^2s^{-1}$
                    • $0.04\,kgm^2s^{-1}$
                    • $0.025\,kgm^2s^{-1}$
                    • $0.01\,kgm^2s^{-1}$
                    CBSE CLASS XII Previous Year Papers

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