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

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Q.1. Which of the following materials is most elastic?
(a) Steel (b) Rubber
(c) Copper (d) Glass

Answer Answer: (a) Young’s modulus of elasticity is highest for steel and Greater the young’s modulus larger is its elasticity.

Q.2. The property of a body by virtue of which it tends to regain its original size and shape when the applied force is removed is called
(a) elasticity (b) plasticity
(c) rigidity (d) compressibility

Q.3. In magnitude hydraulic stress is equal to
(a) hydraulic force (b) hydraulic pressure
(c) restoring force (d) hydraulic strain

Q.4. Substances which can be stretched to cause large strains are called
(a) brittle (b) ductile
(c) plastic (d) elastomer

Q.5. Shearing stress change ____________ of the body.
(c) shape (d) volume

Q.6. The reason for the change in shape of a regular body is
(a) volume stress (b) shearing strain
(c) longitudinal strain (d) metallic strain

Q.7. Shearing strain is expressed by
(a) angle of shear (b) angle of twist
(c) decrease in volume (d) increase in volume

Q.8. The restoring force per unit area is known as
(a) strain (b) elasticity
(c) stress (d) plasticity

Q.9. Which of the following substance has the lowest elasticity?
(a) Steel (b) Copper
(c) Rubber (d) wood

Q.10. 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 above

Answer Answer: (d) The hammering increases elasticity while annealing decreases it. The increase in temperature increases the elasticity while decrease in temperature decreases it. The impurity in the substance increases the elasticity.

Q.11. When forces are applied on a body such that it is still in static equilibrium, then the extent to which the body gets deformed, depends on
(a) nature of the material
(b) magnitude of deforming force
(c) Both (a) & (b)
(d) None of these

Answer Answer: (c) The deformation of a body on application of a force depends on the nature of the material and the magnitude of the applied force.

Q.12. If the load is increased beyond the _ point, the strain increases rapidly for even a small change in the stress.
(a) elastic point (b) yield point
(c) plastic point (d) fracture point

Answer Answer: (b) Yield point is the point, beyond which the wire starts showing increase in strain without any increase in stress.

Q.13. What is the phenomenon of temporary delay in regaining the original configuration by an elastic body, after the removal of a deforming force?
(a) Elastic fatigue (b) Elasticity
(c) Plasticity (d) Elastic after effect

Answer Answer: (d) Elastic after effect is defined as the temporary delay in regaining the original configuration by an elastic body after the removal of a deforming force.

Q.14. Which of the following is not a type of stress?
(a) Tensile stress (b) Compressive stsress
(c) Hydraulic stress (d) None of these

Answer Answer: (d) A cylinder stretched by two equal forces applied normal to its cross-sectional area, it experiences tensile stress; & if cylinder is compressed under the action of applied forces, the restoring force per unit area is known as compressive stress.
A body immersed in a fluid develops restoring force equal & opposite to the forces applied by fluid. This restoring force per unit area is hydraulic stress.

Q.15. Which of the following elastic moduli is used to describe the elastic behaviour of object as they respond to the deforming forces acting on them?
(a) Young’s modulus (b) Shear modulus
(c) Bulk modulus (d) All of these

Answer Answer: (d) The three elastic moduli viz young’s modulus, shear modulus and bulk modulus are used to describe the elastic behavior of objects as they respond to deforming forces acting on them.

Q.16. A rubber cord of cross sectional area 1 mm² and unstretched length 10 cm is stretched to 12 cm and then released to project a stone of mass 5 gram. If Y for rubber = 5 x 108 N/m², then the tension in the rubber cord is
(a) 25 N
(b) 50 N
(c) 100 N
(d) 200 N

Q.17. Which of the following types of stress causes no change in shape?
(a) Compressive stress (b) Hydraulic stress
(c) Shearing stress (d) None of these

Answer Answer: (b) Hydraulic stress is relevant to volumetric strain, 􀀧V/V, but there is no change in shape.

Q.18. Hooke’s law essentially defines
(a) Stress
(b) Strain
(c) Yield point
(d) Elastic limit

Q.19. Two wires have the same material and length, but their masses are in the ration of 4 : 3. If they are stretched by the same force, their elongations will be in the ratio of
(a) 2 : 3
(b) 3 : 4
(c) 4 : 3
(d) 9 : 16

Q.20. Longitudinal strain is possible in the case of
(a) Gases
(b) Liquid
(c) Only solids
(d) Only gases & liquids

Q.21. A body of mass 1 kg is attached to one end of a wire and rotated in horizontal circle of diameter 40 cm with a constant speed of 2 m/s. what is the area of cross-section of the wire if the stress developed in the wire is 5 × 106 N/m²?
(a) 2 mm²
(b) 3 mm²
(c) 4 mm²
(d) 5 mm²

Q.22. Out of the following materials, whose elasticity is independent of temperature?
(a) Copper
(b) Invar steel
(c) Brass
(d) Silver

Q.23. In a wire, when elongation is 2 cm energy stored is E. if it is stretched by 10 cm, then the energy stored will be
(a) E
(b) 2 E
(c) 4 E
(d) 25 E

Q.24. An iron bar of length l m and cross section A m² is pulled by a force of F Newton from both ends so as to produce and elongation in meters. Which of the following statement statements is correct
(a) Elongation is inversely proportional to length l
(b) Elongation is directly proportional to cross section A
(c) Elongation is inversely proportional to A
(d) Elongation is directly proportional to Youngs modulus

Q.25. The ratio of the change in dimension at right angles to the applied force to the initial dimension is known as
(a) Youngs modulus
(b) Poissons ratio
(c) Lateral strain
(d) Shearing strain

Q.26. Two wires A and B are of the same length. The diameters are in the ratio 1 : 2 and the Youngs modulus are in ratio 2 : 1. if they are pulled by the same force, then their elongations will be in ratio
(a) 4 : 1
(b) 1 : 4
(c) 1 : 2
(d) 2 : 1

Q.27. The magnitude of the force developed by raising the temperature from 0°C to 100°C of the iron bar of 1.00 m long and 1 cm² cross-section when it is held so that it is not permitted to expand or bend is (Temperature Co-efficient = 10-5/oC and Y = 1011 N/m²)
(a) 103 N
(b) 104 N
(c) 105 N
(d) 109 N

Q.28. Four wires whose lengths and diameter respectively are given below are made of the same material. Which of these will have the largest extension when same tension is applied?
(a) 0.50 m, 0.50 mm
(b) 1.00 mm, 1.00 mm
(c) 2.00 m, 2.00 mm
(d) 4.00 m, 4.00 mm

Q.29. When the intermolecular distance increases due to tensile force, then
(a) There is no force between the molecules
(b) There is a repulsive force between the molecules
(c) There is an attractive force between the molecules
(d) There is zero resultant force between the molecules

Q.30. The upper end of wire 1 m long and 2 mm radius is clamped. The lower end is twisted through an angle of 45°. The angle of shear is
(a) 0.09°
(b) 0.9°
(c) 9°
(d) 90°

Q.31. One end of a steel wire of area of cross-section 3 mm² is attached to the ceiling of an elevator moving up with an acceleration of 2.2 m/s². if a load of 8 kg is attached at its free end, then the stress developed in the wire will be
(a) 8 × 106 N/m²
(b) 16 × 106 N/m²
(c) 20 × 106 N/m²
(d) 32 × 106 N/m²

Q.32. The radii of two wires of a same material are in ratio 2 : 1. if the wires are stretched by equal forces, the stress produced in them will be
(a) 2 : 1
(b) 4 : 1
(c) 1 : 4
(d) 1 : 2

Q.33. The ratio of the change in dimension at right angles to the applied force to the initial dimension is known as
(a) Youngs modulus
(b) Poissons ratio
(c) Lateral strain
(d) Shearing strain