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NCERT Solutions for class 11 Physics | Chapter 9 - Mechanical Properties of Solids

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Free download in PDF Class 11 Physics Chapter 9 Mechanical Properties of Solids Multiple Choice Questions and Answers for Board, JEE, NEET, AIIMS, JIPMER, IIT-JEE, AIEE and other competitive exams. MCQ Questions for Class 11 Physics with Answers were prepared based on the latest exam pattern. These short solved questions or quizzes are provided by Gkseries. These will help the students for preparation of their examination./p>

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(1) A copper and a steel wire of the same diameter are connected end to end. A deforming force F is applied to this composite wire which causes a total elongation of 1 cm. The two wires will have
[A] the same stress
[B] different stress
[C] the same strain
[D] different strain
Answer: A, D
(2) For an ideal liquid
[A] the bulk modulus is infinite
[B] the bulk modulus is zero
[C] the shear modulus is infinite
[D] the shear modulus is zero
Answer: A, D
(3) A wire is suspended from the ceiling and stretched under the action of a weight F suspended from its other end. The force exerted by the ceiling on it is equal and opposite to the weight.
[A] tensile stress at any cross-section A of the wire is F/A
[B] tensile stress at any cross-section is zero
[C] tensile stress at any cross-section A of the wire is 2F/A
[D] tension at any cross-section A of the wire is F
Answer: A, D
(4) The stress-strain graphs for the two materials are shown in the figure.
[A] material (ii) is more elastic than material (i) and hence material (ii) is more brittle
[B] material (i) and (ii) have the same elasticity and the same brittleness
[C] material (ii) is elastic over a larger region of strain as compared to (i)
[D] material (ii) is more brittle than material (i)
Answer: C, D
(5) Consider two cylindrical rods of identical dimensions, one of rubber and the other of steel. Both the rods are fixed rigidly at one end to the roof. A mass M is attached to each of the free ends at the centre of the rods.
[A] both the rods will elongate but there shall be no perceptible change in shape
[B] the steel rod will elongate and change shape but the rubber rod will only elongate
[C] the steel rod will elongate without any perceptible change in shape, but the rubber rod will elongate and the shape of the bottom edge will change to an ellipse
[D] the steel rod will elongate, without any perceptible change in shape, but the rubber rod will elongate with the shape of the bottom edge tapered to a tip at the centre
Answer: the steel rod will elongate, without any perceptible change in shape, but the rubber rod will elongate with the shape of the bottom edge tapered to a tip at the centre
(6) A spring is stretched by applying a load to its free end. The strain produced in the spring is
[A] volumetric
[B] shear
[C] longitudinal and shear
[D] longitudinal
Answer: longitudinal and shear
(7) The temperature of a wire is doubled. The Young’s modulus of elasticity
[A] will also double
[B] will become four times
[C] will remain same
[D] will decrease
Answer: will decrease
(8) The maximum load a wire can withstand without breaking when its length is reduced to half of its original length, will
[A] be doubled
[B] be half
[C] be four times
[D] remain same
Answer: remain same
(9) Modulus of rigidity of ideal liquid is
[A] infinity
[B] zero
[C] unity
[D] some finite small non-zero constant value
Answer: zero
(10) A copper and a steel wire of the same diameter are connected end to end. A deforming force F is applied to this composite wire which causes a total elongation of 1cm. The two wires will have
[A] the same stress.
[B] different stress.
[C] the same strain.
[D] different strain.
Answer: A, D
(11) 9A rod of length l and negligible mass is suspended at its two ends by two wires of steel (wire A) and aluminium (wire B) of equal lengths (Fig. in below). The cross-sectional areas of wires A and B are 1.0 mm2 and 2.0 mm2, respectively.
(YAl 70 * 109 Nm– 2 and Ysteel 200 * 109 Nm-2

[A] Mass m should be suspended close to wire A to have equal stresses in both the wires.
[B] Mass m should be suspended close to B to have equal stresses in both the wires.
[C] Mass m should be suspended at the middle of the wires to have equal stresses in both the wires.
[D] Mass m should be suspended close to wire A to have equal strain in both wires.
Answer: B, D
(12) The stress-strain graphs for two materials are shown in Fig. below (assume same scale)

[A] Material (ii) is more elastic than material (i) and hence material (ii) is more brittle.
[B] Material (i) and (ii) have the same elasticity and the same brittleness.
[C] Material (ii) is elastic over a larger region of strain as compared to (i).
[D] Material (ii) is more brittle than material (i).
Answer: C, D
(13) A rectangular frame is to be suspended symmetrically by two strings of equal length on two supports (Fig. in below). It can be done in one of the following three ways;

The tension in the strings will be

[A] the same in all cases.
[B] least in (a).
[C] least in (b).
[D] least in (c).
Answer: least in (b).
(14) A mild steel wire of length 2L and cross-sectional area A is stretched, well within elastic limit, horizontally between two pillars (Fig. in below). A mass m is suspended from the mid point of the wire. Strain in the wire is

[A] x2 / 2 L2
[B] x / L
[C] x2 / L
[D] x22 / 2 L
Answer: x2 / 2 L2
(15) 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] (a)
[B] (b)
[C] (c)
[D] (d)
Answer: (b)
(16) The maximum load a wire can withstand without breaking, when its length is reduced to half of its original length, will
[A] be double.
[B] be half.
[C] be four times.
[D] remain same.
Answer: remain same.
(17) Modulus of rigidity of ideal liquids is
[A] infinity.
[B] zero.
[C] unity.
[D] some finite small non-zero constant value.
Answer: zero
(18) Streamline flow is more likely for liquids with
[A] low density and high viscosity
[B] low density and high viscosity
[C] high density and high viscosity
[D] high density and high viscosity
Answer: low density and high viscosity
(19) The Poisson’s ratio of a material is 0.5. If a force is applied to a wire of this material, there is a decrease in the cross-sectional area by 4%. The percentage increase in the length is
[A] 4%
[B] 2.5%
[C] 2%
[D] 1%
Answer: 4%
(20) In Bernoulli’s theorem which of the following is conserved?
[A] Energy
[B] Mass
[C] Linear momentum
[D] Angular momentum
Answer: Energy

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