CBSE Class 11 Physics Mechanical Properties of Solids MCQs Set B

Question: The approximate depth of an ocean is 2700 m.The compressibility of water is 45.4 × 10^–11 Pa^–1 and density of water is 103 kg/m³. What fractional compression of water will be obtained at the bottom of the ocean?
a) 1.2 × 10^–2
b) 1.4 × 10^–2
c) 0.8 × 10^–2
d) 1.0 × 10^–2
Answer: a

Question: A body of mass 10 kg is attached to a wire of radius 3 cm. It’s breaking stress is 4.8 × 107 Nm^–2, the area of cross-section of the wire is 10^–6 m². What is the maximum angular velocity with which it can be rotated in the horizontal circle ?
a) 1 rad sec^–1
b) 2 rad sec^–1
c) 4 rad sec^–1
d) 8 rad sec^–1
Answer: 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 the options
Answer: c

Question: The following four wires of length L and radius r are made of the same material. Which of these will have the largest extension, when the same tension is applied?
a) L = 100 cm, r = 0.2 mm
b) L = 200 cm, r = 0.4 mm
c) L = 300 cm, r = 0.6 mm
d) L = 400 cm, r = 0.8 mm
Answer: a

Question: Which of the following affects the elasticity of a substance?
a) hammering and annealing
b) change in temperature
c) impurity in substance
d) All of the options
Answer: d

Question: The radii and Young’s moduli of two uniform wires A and B are in the ratio 2 : 1 and 1 : 2 respectively. Both wires are subjected to the same longitudinal force. If the increase in length of the wire A is one percent, the percentage increase in length of the wire B is
a) 1.0
b) 1.5
c) 2.0
d) 3.0
Answer: c

Question: Two wires A and B have the same length and area of cross-section. But Young’s modulus of A is two times the Young’s modulus of B. Then the ratio of force constant of A to that of B is
a) 1
b) 2
c) 1/2
d) √2
Answer: b

Question: The volume change of a solid copper cube 10 cm on an edge, when subjected to a pressure of 7 MPa is (Bulk modulus of copper = 140 GPa)
a) 5 × 10^–2 cm³
b) 10 × 10^–2 cm³
c) 15 × 10^–2 cm³
d) 20 × 10^–2 cm³
Answer: a

Question: When a pressure of 100 atmosphere is applied on a spherical ball, then its volume reduces to 0.01%. The bulk modulus of the material of the rubber in dyne/cm2 is
a) 10 × 10¹²
b) 100 × 10¹²
c) 1 × 10¹²
d) 10 × 10¹²
Answer: c

Question: Two wires are made of the same material and have the same volume. However wire 1 has cross-sectional area A and wire 2 has crosssectional area 3A. If length of wire l is increased by Δx on applying force F, how much force is needed to stretch wire 2 by the same amount?
a) 4F
b) 6F
c) 9F
d) F
Answer: c

Question: Two wires of same material and length but cross-sections in the ratio 1 : 2 are used to suspend the same loads. The extensions in them will be in the ratio
a) 1 : 2
b) 2 : 1
c) 4 : 1
d) 1 : 4
Answer: b

Question: The Young’s modulus of a perfectly rigid body is
a) unity
b) zero
c) infinity
d) some finite non-zero constant
Answer: c

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 = 200 cm, diameter = 2 mm
b) length = 300 cm, diameter = 3 mm
c) length = 50 cm, diameter = 0.5 mm
d) length = 100 cm, diameter = 1 mm
Answer: c

Question: A mild steel wire of length 2L and crosssectional area A is stretched, well within elastic limit, horizontally between two pillars as shown in the figure. A mass m is suspended from the mid‑point of the wire. Strain in the wire is

a) x2/2L2
b) x/L
c) x2/L
d) x2/2L
Answer: 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 options
Answer: d

Question: A wire of length L and radius r fixed at one end and a force F applied to the other end produces an extension l. The extension produced in another wire of the same material of length 2 L and radius 2r by a force 2F, is
a) ∫
b) 2∫
c) 4∫
d) ∫/2
Answer: a

Question: Copper of fixed volume V is drawn into wire of length l. When this wire is subjected to a constant force F, the extension produced in the wire is Dl. Which of the following graphs is a straight line?
a) Dl versus 1/l
b) Dl versus l 2
c) Dl versus 1/l 2
d) Dl versus l
Answer: b

Question: Two blocks of masses 1 kg and 2 kg are connected by a metal wire going over a smooth pulley as shown in figure. The breaking stress of the metal is (40/3π) × 10⁶ N/m2. If g = 10 m s^–2, then the minimum radius of the wire used if it is not to break is

a) 0.5 mm
b) 1 mm
c) 1.5 mm
d) 2 mm
Answer: b

Question: K is the force constant of a spring. The work done in increasing its extension from l₁ to l₂ will be
a) K(l₂ – l₁)
b) K/2(l₂ + l₁)
c) K(l₂² – l₁²)
d) K/2(l₂² + l₁²)
Answer: d

Question: Minimum and maximum values of Possion’s ratio for a metal lies between
a) – ∞ to + ∞
b) 0 to 1
c) – ∞ to 1
d) 0 to 0.5
Answer: d

Question: In solids interatomic forces are
a) totally repulsive
b) totally attractive
c) both totally repulsive and totally attractive
d) None of the options
Answer: c

Question: A solid sphere of radius R, made of a material of bulk modulus K, is surrounded by a liquid in a cylindrical container. A massless piston of area A floats on the surface of the liquid. When a mass M is placed on the piston to compress the liquid the fractional change in the radius of the sphere dR/R, is
a) Mg/2AK
b) Mg/3AK
c) Mg/AK
d) 2Mg/3AK
Answer: b

Question: A and B are two wires. The radius of A is twice that of B.
They are stretched by the same load. Then the stress on B is
a) equal to that on A
b) four times that on A
c) two times that on A
d) half that on A
Answer: b

Question: The length of an elastic spring is a metres when a force of 4 N is applied, and b metres when the 5 N force is applied. Then the length of the spring when the 9 N force is applied is
a) a + b
b) 9b – 9a
c) 5b – 4a
d) 4a – 5b
Answer: c

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 the options
Answer: c

Question: The Young’s modulus of brass and steel are respectively 1.0 × 10¹¹ N m^–2 and 2.0 × 1011 N m^–2. A brass wire and a steel wire of the same length are extended by 1 mm each under the same force. If radii of brass and steel wires are RB and RS respectively, then
a) RS = √2RB
b) RS = RB/√2
c) RS = 4RB
d) RS = RB/2
Answer: b

Question: The bulk modulus of water if its volume changes from 100 litre to 99.5 litre under a pressure of 100 atm is
(Take 1 atm = 105 N m^–2)
a) 2 × 107 N m^–2
b) 2 × 108 N m^–2
c) 2 × 109 N m^–2
d) 2 × 1010 N m^–2
Answer: c

Question: Two wires A and B of the same material have their lengths in the ratio of 1 : 2 and their diameters in the ratio of 2 : 1. If they are stretched with the same force, the ratio of the increase in the length of A to that of B will be
a) 1 : 2
b) 4 : 1
c) 1 : 8
d) 1 : 4
Answer: c

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
Answer: 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) 4 : 1
b) 1 : 1
c) 1 : 2
d) 2 : 1
Answer: d