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 solids, Hooke’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

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.

$Poisson's\ Ratio\ = {Lateral\ strain \over Longitudinal\ Strain}$

Class 11 Physics Chapter 9 Related Guides –

Stress and Strain	Elastic Moduli	Shear Modulus
Bulk Modulus	Shearing Stress	Yield Strength
Elastic Limit	Tensile Stress	Elastomers
Beam Deflection Formula	Solid Deformation	Stress Formula

Class 11 Physics Study Guides:

Difference between in Physics	Physics Formula	Class 11 Physics Notes
Relation between articles in Physics	Derivations in Physics	Physics Study Notes
NCERT Solutions for Class 11 Physics	Physics Constants	SI Units in Physics

CBSE CLASS XII Related Questions

1.
A parallel plate capacitor has plate area $ A $ and plate separation $ d $. Half of the space between the plates is filled with a material of dielectric constant $ K $ in two ways as shown in the figure. Find the values of the capacitance of the capacitors in the two cases.
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2.
The resistance of a wire at 25°C is 10.0 $ \Omega $. When heated to 125°C, its resistance becomes 10.5 $ \Omega $. Find (i) the temperature coefficient of resistance of the wire, and (ii) the resistance of the wire at 425°C.
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3.
A system of two conductors is placed in air and they have net charge of $ +80 \, \mu C $ and $ -80 \, \mu C $ which causes a potential difference of 16 V between them.
(1) Find the capacitance of the system.
(2) If the air between the capacitor is replaced by a dielectric medium of dielectric constant 3, what will be the potential difference between the two conductors?
(3) If the charges on two conductors are changed to +160µC and −160µC, will the capacitance of the system change? Give reason for your answer.
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4.
The ends of six wires, each of resistance R (= 10 $\Omega$) are joined as shown in the figure. The points A and B of the arrangement are connected in a circuit. Find the value of the effective resistance offered by it to the circuit.
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5.
Figure shows variation of Coulomb force (F) acting between two point charges with $ \frac{1}{r^2} $, $ r $ being the separation between the two charges $ (q_1, q_2) $ and $ (q_2, q_3) $. If $ q_2 $ is positive and least in magnitude, then the magnitudes of $ q_1, q_2 $, and $ q_3 $ are such that:
- $ q_2<q_1<q_3 $
- $ q_3<q_1<q_2 $
- $ q_1<q_2<q_3 $
- $ q_2<q_3<q_1 $
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6.
A rectangular glass slab ABCD (refractive index 1.5) is surrounded by a transparent liquid (refractive index 1.25) as shown in the figure. A ray of light is incident on face AB at an angle $i$ such that it is refracted out grazing the face AD. Find the value of angle $i$.
$A rectangular glass slab ABCD (refractive index 1.5)$
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