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Class 11 Physics Objective Chapter – 9 Mechanical Properties of Solids
1. A member which does not regain its original shape after removal of the load producing deformation is said ______
( a ) Plastic
( b ) Elastic
( c ) Rigid
( d ) None of these
Ans:- (a)
2. 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
Ans:- (c)
3.The fractional change in volume per unit increase in the pressure is called :
( a ) Volume coefficient
( b ) Pressure gradient
( c ) Compressibility
( d ) Bulk modulus
Ans:- (c)
4.The breaking stress for wire of unit area of cross-section is called its
( a ) Young’s modulus
( b ) tensile strength
( c ) yield point
( d ) elastic limit
Ans:- (b)
5. 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
Ans:- (d)
6. A steel wire of length 20 cm and uniform cross-section 1mm2 is tied rigidly at both the ends. The temperature of the wire is altered from 40ºC to 20ºC. Coefficient of linear expansion for steel a = 1.1 × 10–5/ºC and Y for steel is 2.0 × 1011 N/m2. The change in tension of the wire is
( a ) 2.2 × 106 newton
( b ) 16 newton
( c ) 8 newton
( d ) 44 newton
Ans:- (d)
7. 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
Ans:- (d)
8. Hookes law essentially defines
( a ) Stress
( b ) Strain
( c ) Yield point
( d ) Elastic limit
Ans:- (d)
9. Which law is also called as the elasticity law?
( a ) Bernoulli’s law
( b ) Stress law
( c ) Hooke’s law
( d ) Poisson’s law
Ans:- (c)
10. Longitudinal strain is possible in the case of
( a ) Gases
( b ) Liquid
( c ) Only solids
( d ) Only gases & liquids
Ans:- (c)
11. You are given two wires W1 and W2. Both are made of the same material and are of the same length. The radius of cross-section of W2 is twice that of W1. Same load is suspended from both of them. If the strain in W1 be 4, then calculate the strain in W2.
( a ) 8
( b ) 4
( c ) 2
( d ) 1
Ans:- (d)
12.If the length of a wire is reduced to half, then it can hold the
( a ) same load
( b ) one fourth load
( c ) half load
( d ) double load
Ans:- (a)
13.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
Ans:- (b)
14. A cube is subjected to a uniform volume compression. If the side of the cube decreases by 2% the bulk strain is
( a ) 0.02
( b ) 0.03
( c ) 0.04
( d ) 0.06
Ans:- (d)
15. 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 ? 108N/m², then the tension in the rubber cord is
( a ) 25 N
( b ) 50 N
( c ) 100 N
( d ) 200 N
Ans:- (c)
16. A body of mass 500 g is fastened to one end of a steel wire of length 2 m and area of cross section 2 mm². if the breaking stress of he wire is 1.25 × 107 N/m², then the maximum angular velocity with which the body can be rotated in a horizontal circle is
( a ) 2 rad/s
( b ) 3 rad/s
( c ) 4 rad/s
( d ) 5 rad/s
Ans:- (d)
17. Modulus of rigidity of ideal liquid is
( a ) infinity
( b ) zero
( c ) unity
( d ) some finite small non-zero constant value
Ans:- (b)
18. Out of the following materials, whose elasticity is independent of temperature?
( a ) Copper
( b ) Invar steel
( c ) Brass
( d ) Silver
Ans:- (b)
19.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 same material of length 2L and radius 2r by a force 2F is given by
( a ) l
( b ) 2l
( c ) l/2
( d ) 4l
Ans:- (a)
20.The substance which shows no elastic after effect practically is
( a ) steel
( b ) rubber
( c ) copper
( d ) quartz
Ans:- (d)
21. A rubber cord of cross sectional area 1mm² 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 ? 108N/m², then the tension in the rubber cord is
( a ) 25 N
( b ) 50 N
( c ) 100 N
( d ) 200 N
Ans:- (c)
22.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
Ans:- (d)
23.Out of the following materials, whose elasticity is independent of temperature?
( a ) Copper
( b ) Invar steel
( c ) Brass
( d ) Silver
Ans:- (b)
24.If a material is heated and annealed, then its elasticity is
( a ) Increased
( b ) Decreased
( c ) Not change
( d ) Becomes zero
Ans:- (b)
25.Longitudinal strain is possible in the case of
( a ) Gases
( b ) Liquid
( c ) Only solids
( d ) Only gases & liquids
Ans:- (c)
26.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
( b ) Elongation is directly proportional to cross section A
( c ) Elongation is inversely proportional to A
( d ) Elongation is directly proportional to Youngs modulus
Ans:- (c)
27. A steel wire is loaded by 2 kg weight. If the radius of the wire is doubled, then its extension will become
( a ) half
( b ) four times
( c ) one-fourth
( d ) double
Ans:- (c)
28.The change in the shape of a regular boy is due to
( a ) Bulk strain
( b ) Shearing strain
( c ) Longitudinal strain
( d ) Volume strain
Ans:- (b)
29. Out of the following materials, whose elasticity is independent of temperature
( a ) Copper
( b ) Invar steel
( c ) Brass
( d ) Silver
Ans:- (b)
30.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
Ans:- (a)
31. 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
Ans:- (c)
32. 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
Ans:- (c)
33.When impurities are added to an elastic substance, its elasticity
( a ) Increases
( b ) Decreases
( c ) Becomes zero
( d ) Remains constant
Ans:- (a)
34.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
Ans:- (c)
35.A cable breaks if stretched by more than 2 mm. It is cut into two equal parts. By how much either part can be stretched without breaking?
( a ) 2mm
( b ) 1 mm
( c ) 0.5 mm
( d ) 0.25 mm
Ans:- (b)
36.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
Ans:- (c)
37.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
Ans:- (c)
38.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
( a ) 4 × 103 N
( b ) 16 × 103 N
( c ) 1/4 x 103 N
( d ) 1/16 x 103N
Ans:- (b)
39.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
Ans:- (a)
40. A wire suspended vertically from one of its ends is stretched by attaching a weight of 100N to its lower end. What is the elastic potential energy stored in the wire, if the weight stretches the wire by 1.5 mm?
( a ) 5 × 10-2 J
( b ) 10-3 J
( c ) 2.5 × 10-3 J
( d ) 7.5 × 10-2 J
Ans:- (d)
41. Shearing strain is expressed by
( a ) angle of shear
( b ) decrease in volume
( c ) angle of twist
( d ) increase in volume
Ans:- (a)
42. 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
Ans:- (a)
43.In the following data, the fou r wires made of the same material have length L and radius r. Which 6f these will have the maximum extension when the same force is applied?
( a ) L = 50 cm, r = 0.4 mm
( b ) L = 100 cm, r = 1 mm
( c ) L = 200 cm, r = 2 mm
( d ) L = 300 cm, r = 3 mm
Ans:- (a)
44.In magnitude hydraulic stress is equal to
( a ) hydraulic pressure
( b ) hydraulic strain
( c ) hydraulic force
( d ) restoring force
Ans:- (a)
45.If the length of a wire is reduced to half, then it can hold the
( a ) same load
( b ) one fourth load
( c ) half load
( d ) double load
Ans:- (a)
46.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
Ans:- (a)
47.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
Ans:- (c)
48.Theoretical value of Poissions ratio lies between
( a ) -1 to 0.5
( b ) -1 to -2
( c ) 0.5 to 1
( d ) None
Ans:- (a)
49. The property by which a body returns to its original shape after removal of the force is called ______
( a ) Plasticity
( b ) Elasticity
( c ) Ductility
( d ) Malleability
Ans:- (b)
50. 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
Ans:- (d)
