# MCQ Questions Chapter 9 Mechanical Properties of Solids Class 11 Physics

Please refer to MCQ Questions Chapter 9 Mechanical Properties of Solids Class 11 Physics with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 11 Physics issued for the current academic year. We have provided MCQ Questions for Class 11 Physics for all chapters on our website. Students should learn the objective based questions for Chapter 9 Mechanical Properties of Solids in Class 11 Physics provided below to get more marks in exams.

## Chapter 9 Mechanical Properties of Solids MCQ Questions

Please refer to the following Chapter 9 Mechanical Properties of Solids MCQ Questions Class 11 Physics with solutions for all important topics in the chapter.

MCQ Questions Answers for Chapter 9 Mechanical Properties of Solids Class 11 Physics

Question. Elastomers are the materials which
(a) are not elastic at all
(b) have very small elastic range
(c) do not obey Hooke’s law
(d) None of these

C

Question. In solids interatomic forces are
(a) totally repulsive
(b) totally attractive
(c) both (a) and (b)
(d) None of these

C

Question. According to Hooke’s law of elasticity, if stress is increased, then the ratio of stress to strain
(a) becomes zero
(b) remains constant
(c) decreases
(d) increases

B

Question. Which one of the following is not a unit of Young’s modulus ?
(a) Nm–1
(b) Nm–2
(d) dyne cm–2
(d) mega pascal

A

Question. A force of 103 newton, stretches the length of a hanging wire by 1 millimetre. The force required to stretch a wire of same material and length but having four times the diameter by 1 millimetre is

B

Question. In case of steel wire (or a metal wire), the limit is reached when
(a) the wire just break
(b) the load is more than the weight of wire
(c) elongation is inversely proportional to the tension
(d) None of these

D

Question. When an elastic material with Young’s modulus Y is subjected to stretching stress S, elastic energy stored per unit volume of the material is
(a) YS / 2
(b) S2Y / 2
(c) S2 / 2Y
(d) S / 2Y

C

Question. The Young’s modulus of steel is twice that of brass. Two wires of same length and of same area of cross section, one of steel and another of brass are suspended from the same roof. If we want the lower ends of the wires to be at the same level, then the weights added to the steel and brass wires must be in the ratio of :
(a) 2 : 1
(b) 4 : 1
(c) 1 : 1
(d) 1 : 2

A

Question. The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied ?
(a) Length = 100 cm, diameter = 1 mm
(b) Length = 200 cm, diameter = 2 mm
(c) Length = 300 cm, diameter = 3 mm
(d) Length = 50 cm, diameter = 0.5 mm

D

Question. The upper end of a wire of diameter 12mm and length 1m is clamped and its other end is twisted through an angle of 30°. The angle of shear is
(a) 18°
(b) 0.18°
(c) 36°
(d) 0.36°

B

Question. A rubber cord catapult has cross-sectional area 25 mm2 and initial length of rubber cord is 10 cm. It is stretched to 5 cm and then released to project a missile of mass 5 gm. Taking Yrubber = 5 × 108 N/m2. Velocity of projected missile is
(a) 20 ms–1
(b) 100 ms–1
(c) 250 ms–1
(d) 200 ms–1

C

Question. K is the force constant of a spring. The work done in increasing its extension from l1 to l2 will be

D

Question. A beam of metal supported at the two edges is loaded at the centre. The depression at the centre is proportional to
(a) Y2
(b) Y
(c) 1/Y
(d) 1/Y2

C

Question. The compressibility of water is 4 × 10–5 per unit atmospheric pressure. The decrease in volume of 100 cm3 of water under a pressure of 100 atmosphere will be
(a) 0.4 cm3
(b) 4 × 10–5 cm3
(c) 0.025 cm3
(d) 0.004 cm3

A

Question. A wire suspended vertically from one of its ends is stretched by attaching a weight of 200N to the lower end. The weight stretches the wire by 1 mm. Then the elastic energy stored in the wire is
(a) 0.2 J
(b) 10 J
(c) 20 J
(d) 0.1 J

D

Question. A steel ring of radius r and cross sectional area A is fitted onto a wooden disc of radius R (R > r). If the Young’s modulus of steel is Y, then the force with which the steel ring is expanded is
(a) A Y (R/r)
(b) A Y (R – r)/r
(c) (Y/A)[(R – r)/r]
(d) Y r/A R

B

Question. The load versus elongation graph for four wires is shown. The thinnest wire is

(a) P
(b) Q
(c) R
(d) S

B

Question. Uniform rod of mass m, length l , area of cross-section A has Young’s modulus Y. If it is hanged vertically, elongation under its own weight will be

C

Question. Which of the following has no dimensions ?
(a) strain
(b) angular velocity
(c) momentum
(d) angular momentum

A

Question. Which one of the following affects the elasticity of a substance ?
(a) Change in temperature
(b) Hammering and annealing
(c) Impurity in substance
(d) All of the above

D

Question. Which of the following relation is true ?

D

Question. A metal rod of Young’s modulus 2 × 1010 N m–2 undergoes an elastic strain of 0.06%. The energy per unit volume stored in J m–3 is
(a) 3600
(b) 7200
(c) 10800
(d) 14400

A

Question. For the same cross-sectional area and for a given load, the ratio of depressions for the beam of a square cross-section and circular cross-section is
(a) 3 : π
(b) π : 3
(c) 1 : π
(d) π : 1

A

Question. An iron rod of length 2m and cross-sectional area of 50 mm2 stretched by 0.5 mm, when a mass of 250 kg is hung from its lower end. Young’s modulus of iron rod is
(a) 19.6´1020 N/m2
(b) 19.6´1018 N/m2
(c) 19.6´1010 N/m2
(d) 19.6´1015 N/m2

C

Question. If a rubber ball is taken at the depth of 200 m in a pool, its volume decreases by 0.1%. If the density of the water is 1 × 103 kg/m3 and g = 10m/s2, then the volume elasticity in N/m2 will be
(a) 108
(b) 2 × 108
(c) 109
(d) 2 × 109

D

Question. The potential energy U between two atoms in a diatomic molecules as a function of the distance x between atoms has been shown in the figure. The atoms are

(a) attracted when x lies between A and B and are repelled when x lies between B and C
(b) attracted when x lies between B and C and are repelled when x lies between A and B
(c) are attracted when they reach B from C
(d) are repelled when they reach B from A

B

Question. A steel wire of uniform cross-section of 1mm2 is heated upto 50°C and clamped rigidly at its ends. If temperature of wire falls to 40°C, change in tension in the wire is (coefficient of linear expansion of steel is 1.1 × 105/°C and Young’s modulus of elasticity of steel is 2 × 1011 N/m2 )
(a) 22 N
(b) 44 N
(c) 88 N
(d) 88 × 106 N

A

Question. A steel rod of radius R = 10 mm and length L= 100 cm is stretched along its length by a force F = 6.28 × 104 N. If the Young’s modulus of steel is Y = 2 ×1011 N/m2, the percentage elongation in the length of the rod is :
(a) 0.100
(b) 0.314
(c) 2.015
(d) 1.549

A

Question. The bulk modulus of a spherical object is ‘B’. If it is subjected to uniform pressure ‘p’, the fractional decrease in radius is
(a) B/3p
(b) 3p/B
(c) p/3B
(d) p/B

C

Question. The ratio of shearing stress to the corresponding shearing strain is called
(a) bulk modulus
(b) Young’s modulus
(c) modulus of rigidity
(d) None of these

C

Question. A force of 6 × 106 N m–2 required for breaking a material. The density r of the material is 3 × 103 kg m–3. If the wire is to break under its own weight, then the length of the wire made of that material should be (Given, g = 10 m s–2)
(a) 20 m
(b) 200 m
(c) 100 m
(d) 2000 m

B

Question. A steel wire of length 4.5 m and crosssectional area 3 × 10–5 m2 stretches by the same  amount as a copper wire of length 3.5 m and cross-sectional area of 4 × 10–5 m2 under a given load. The ratio of the Young’s modulus of steel to that of copper is
(a) 1.3
(b) 1.5
(c) 1.7
(d) 1.9

C

Question. A rigid bar of mass M is supported symmetrically by three wires each of length L. Those at each end are of copper and the middle one is of iron. The ratio of their diameters, if each is to have the same tension, is equal to
(a) Y∝pper/Yiron
(b) √Yiron/Y∝pper
(c) Y2iron/Y2∝pper
(d) Yiron/Y∝pper

B

Question. The given graph shows the extension (Δ∫) of a wire of length 1 m suspended from the top of a roof at one end and with a load W connected to the other end. If the cross-sectional area of the wire is 10–6 m2, then the Young’s modulus of the material of the wire is

(a) 2 × 1011 N/m2
(b) 2 × 10–11 N/m2
(c) 3 × 10–12 N/m2
(d) 2 × 10–13 N/m

A

Question. Three equal masses of 3 kg are connected by massless string of cross sectional area 0.005 cm2  and Young’s modulus 2 × 1011 N/m2. In the absence of friction, the longitudinal strain in the wire

(a) A is 10–4
(b) B is 2 × 10–4
(c) both (a) and (b)
(d) none of these

C

Question. A glass slab is subjected to a pressure of 10 atm. The fractional change in its volume is (Bulk modulus of glass = 37 × 109 N m–2, 1 atm = 1 × 105 N m–2)
(a) 2.7 × 10–2
(b) 2.7 × 10–3
(c) 2.7 × 10–4
(d) 2.7 × 10–5

D

Question. A steel rod of length 1 m and radius 10 mm is stretched by a force 100 kN along its length. The stress produced in the rod is
(YSteel = 2 × 1011 N m–2)
(a) 3.18 × 106 N m–2
(b) 3.18 × 107 N m–2
(c) 3.18 × 108 N m–2
(d) 3.18 × 109 N m–2

C

Question. A graph between the restoring force (F) of a wire and the extension (x) produced in it, is shown in the figure. Then YA/L (in SI unit) is

(a) 3
(b) 1
(c) 3
(d) 1

A

Question. Four wires of the same material are stretched by the same load. The dimensions are given below. Which of them will elongate the most ?
(a) Length 100 cm, diameter 1 cm
(b) Length 200 cm, diameter 2 cm
(c) Length 300 cm, diameter 3 cm
(d) Length 400 cm, diameter 0.5 cm

D

Question. A light rod of length 200 cm is suspended from the ceiling horizontally by means of two vertical wires of equal length tied to its ends. One of the wires is made of steel and is of crosssection 0.1 cm2 and the other of brass of crosssection 0.2 cm2. Along the rod at which distance a weight may be hung to produce equal stresses in both the wires?
(YSteel = 2 × 1011 N m–2, YBrass = 1 × 1011 N m–2)
(a) 4/3 m from steel wire
(b) 4/3 m from brass wire
(c) 1 m from steel wire
(d) 1/4 m from brass wire

A

Assertion & Reasoning Based MCQs :

Assertion (A) and the other labelled
Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is NOT the correct explanation of A
(c) A is true but R is false
(d) A is false and R is also false

Question. Assertion (A) : Glassy solids have sharp melting point.
Reason (R) : The bonds between the atoms of glassy solids get broken at the same temperature.

D

Question. Assertion (A) : Two identical solid balls, one of ivory and the other of wet-clay are dropped from the same height on the floor. Both the balls will rise to same height after bouncing.
Reason (R) : Ivory and wet-clay have same elasticity.

D

Question. Assertion (A) : Breaking stress is fixed for a material, but breaking force will vary, depending on area of cross section of the wire.
Reason (R) : While using a material, the working stress is always kept much lower than that of  breaking stress so that safety factor (= breaking stress/working stress) may have a large value.

B

Question. Assertion (A) : Strain is a unitless quantity.
Reason (R) : Strain is equivalent to force.

C

Question. Assertion (A) : Young’s modulus for a perfectly plastic body is zero.
Reason (R) : For a perfectly plastic body, restoring force is zero.

A

Question. Assertion (A) : Steel is more elastic than rubber.
Reason (R) : Under given deforming force, steel is deformed less than rubber.

A

Question. Assertion (A) : The crane which is used to lift and move the heavy load is provided with thick and
strong metallic ropes to which the load to be lifted is attached.
Reason (R) : The thickness of the metallic rope used in the crane is decided from the knowledge of elastic limit of the material of the rope and the factor of safety.

B

Question. Assertion (A) : Bulk modulus of elasticity (K) represents incompressibility of the material.
Reason (R) : Bulk modulus of elasticity is proportional to change in pressure.

A

Question. Assertion (A) : Spring balances show incorrect readings after they had been used for a long time interval.
Reason (R) : On using for long time, spring balance loses its elastic strength.

A

Question. Assertion (A) : Identical springs of steel and copper are equally stretched. More work will be done on the steel spring.
Reason (R) : Steel is more elastic than copper.

A

Case Based MCQs :

The graph shown below shows qualitatively the relation between the stress and the strain as the deformation gradually increases. Within Hooke’s limit for a certain region stress and strain relation is linear. Beyond that up to a certain value of strain the body is still elastic and if deforming forces are removed the body recovers its original shape.

Question. During unloading beyond B, say C, the length at zero stress in now equal to
(a) less than original length
(b) greater than original length
(c) original length
(d) can’t be predicted

B

Question. The breaking stress for a wire of unit crosssection is called
(a) yield point
(b) elastic fatigue
(c) tensile strength
(d) Young’s modulus

C

(a) OA only
(b) OB only
(c) OC only
(d) OD only

B

Question. Substances which can be stretched to cause large strains are called
(a) isomers
(b) plastomers
(c) elastomers
(d) polymers

C

Question. If deforming forces are removed up to which point the curve will be retraced?
(a) upto OA only
(b) upto OB
(c) upto C
(d) Never retraced its path

B

Hooke’s law,
According to Hooke’s law, within the elastic limit, the stress applied to a body is directly proportional to the corresponding strain.
Stress ∝ Strain
or Stress = E × Strain or Stress/Strain = E
Where E is the constant of proportionality and is known as coefficient of elasticity or modulus of elasticity.
Hooke’s law is an empirical law and is found to be valid for most materials. However, there are some materials which do not exhibit this linear relationship.

Question. According to Hooke’s law, if stress is reduced to one-third, the ratio of stress to strain
(a) is increased to three time
(b) is decreased
(c) is zero
(d) remains constant.

D

Question. Within elastic limit, which of the following graphs correctly represents the variation of extension in the length of a wire with the external load?

B

Question. Whenever a material is loaded with elasitic limits, stress is ……… strain.
(a) equal to
(b) directly proportional to
(c) inxessely propotional to
(d) None of the above given

B

Question. According to Hooke’s law of elasticity, if stress is increased, the ratio of stress to strain
(a) decreases
(b) increases
(c) becomes zero
(d) remains constant

D

Question. Hooke’s law defines
(a) stress
(b) strain
(c) modulus of elasticity
(d) elastic limit.