Objective Type Questions On Class 11 Physics Chapter 9 Mechanical Properties of Solids

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

View Answer

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

View Answer

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

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Answer:A, D

4 The stress-strain graphs for the two materials are shown in the figure. Mechanical Properties of Solids

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)

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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

View Answer

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.

View Answer

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.
(Y_Al 70 * 10⁹ Nm^{– 2} and Y_steel 200 * 10⁹ Nm^-2

Mechanical Properties of Solids

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.

View Answer

Answer:B, D

12 The stress-strain graphs for two materials are shown in Fig. below (assume same scale)

Mechanical Properties of Solids

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).

View Answer

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;

Mechanical Properties of Solids

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).

View Answer

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

Mechanical Properties of Solids

A x² / 2 L²

B x / L

C x² / L

D x2² / 2 L

View Answer

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

Mechanical Properties of Solids

A (a)

B (b)

C (c)

D (d)

View Answer

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.

View Answer

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.

View Answer

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

View Answer

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%

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