Mechanical Properties of Solids Practice Questions - DPP for NEET

 Page 1


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 Length of a wire is doubled, when 20 × 10
8
 N/m
2
 stress is
applied on it. Its Y oung’s modulus of elasticity in N/m
2
 will
be
(a) 20 × 10
8
(b) 20 × 10
9
(c) 20 × 10
10
(d) 10 × 10
8
Q.2 A steel wire of uniform cross-sectional area 2mm
2
 is heated
upto 50°C and clamped rigidly at two ends. If the
temperature of wire falls to 30° then change in tension in
the wire will be, if coefficient of linear expansion of steel
is 1.1 × 10
–5
 /°C and young's modulus of elasticity of steel
is 2 × 10
11
 N/m
2
.
(a) 44 N (b) 88 N
(c) 132 N (d) 22 N
Q.3 The work done in increasing the length of a one metre long
wire of cross-sectional area 1mm
2
 through 1mm will be
(Y = 2 × 10
11
 N/m
2
)
(a) 250 J (b) 10 J
(c) 5 J (d) 0.1 J
Q.4 A spring is stretched by 3cm when a load of 5.4 × 10
6
 dyne
is suspended from it. Work done will be-
(a) 8.1 × 10
6
 J (b) 8 × 10
6
 J
(c) 8.0 × 10
6
 erg (d) 8.1 ×10
6
 erg
Page 2


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 Length of a wire is doubled, when 20 × 10
8
 N/m
2
 stress is
applied on it. Its Y oung’s modulus of elasticity in N/m
2
 will
be
(a) 20 × 10
8
(b) 20 × 10
9
(c) 20 × 10
10
(d) 10 × 10
8
Q.2 A steel wire of uniform cross-sectional area 2mm
2
 is heated
upto 50°C and clamped rigidly at two ends. If the
temperature of wire falls to 30° then change in tension in
the wire will be, if coefficient of linear expansion of steel
is 1.1 × 10
–5
 /°C and young's modulus of elasticity of steel
is 2 × 10
11
 N/m
2
.
(a) 44 N (b) 88 N
(c) 132 N (d) 22 N
Q.3 The work done in increasing the length of a one metre long
wire of cross-sectional area 1mm
2
 through 1mm will be
(Y = 2 × 10
11
 N/m
2
)
(a) 250 J (b) 10 J
(c) 5 J (d) 0.1 J
Q.4 A spring is stretched by 3cm when a load of 5.4 × 10
6
 dyne
is suspended from it. Work done will be-
(a) 8.1 × 10
6
 J (b) 8 × 10
6
 J
(c) 8.0 × 10
6
 erg (d) 8.1 ×10
6
 erg
2
DPP/ P 20
Q.5 A wire of length 1m and area of cross section 4 × 10
-8
 m
2
increases in length by 0.2 cm when a force of 16 N is applied.
V alue of Y for the material of the wire will be
(a) 2 × 10
6
 N/m
2
(b) 2 × 10
11
 kg/m
2
(c) 2 × 10
11
 N/mm
2
(d) 2 × 10
11
 N/m
2
Q.6 The volume of a solid rubber ball when it is carried from the
surface to the bottom of a 200 m deep lake decreases by
0.1%. The value for bulk modulus of elasticity for rubber will
be
(a) 2 × 10
9
 Pa (b) 2 × 10
6
 Pa
(c) 2 × 10
4
 Pa (d) 2 × 10
–4
 Pa
Q.7 A steel wire is 4.0 m long and 2 mm in diameter. Young’s
modulus of steel is 1.96 × 10
11
 N/m
2
. If a mass of 20 kg is
suspended from it the elongation produced will be -
(a) 2 .5 4 m m (b) 1.27 mm
(c) 0.64 mm (d) 0.27 mm
Q.8 A brass rod is to support a load of 400 N. If its elastic limit is
4.0 × 10
8
 N/m
2
 its minimum diameter must be -
(a) 1.13 mm (b) 2.26 mm
(c) 3.71 mm (d) 4.52 mm
Q.9 A 4.0 m long copper wire of cross sectional area 1.2 cm
2
 is
stretched by a force of 4.8 × 10
3 
N stress will be -
(a) 4.0 × 10
7
 N/mm
2
(b) 4.0 × 10
7
 KN/m
2
(c) 4.0 × 10
7
 N/m
2
(d) None of these
Q.10 A copper rod 2m long is stretched by 1mm. Strain will be -
(a) 10
–4
, volumetric (b) 5 × 10
–4
, volumetric
(c) 5 × 10
–4
, longitudinal (d) 5 × 10
–3
, volumetric
Q.11 A wire of cross sectional area 3mm
2
 is just stretched between
two fixed points at a temperature of 20°C. Determine the
tension when the temperature falls to 20°C. Coefficient of
linear expansion a = 10
–5
 /°C and Y = 2 × 10
11
 N/m
2
.
(a) 120 KN (b) 20 N (c) 120 N (d) 102 N
Q.12 The compressibility of water is 5 × 10
–10
 m
2
/N. If it is
subjected to a pressure of 15 MPa, the fractional decrease in
volume will be -
(a) 3.3 × 10
–5
(b) 5.6 × 10
–4
(c) 7.5 × 10
–3
(d) 1.5 × 10
–2
Q.13 The Young’s modulus of steel is 2 × 10
11
 N/m
2
 and its
coefficient of linear expansion is 1.1 × 10
–5 
per deg. The
pressure  to be applied to the ends of a steel cylinder to
keep its length constant on raising its temperature by 100ºC,
will be -
(a) 5.5 × 10
4
 N/m
2
(b) 1.8 × 10
6
 N/m
2
(c) 2.2 × 10
8
 N/m
2
(d) 2.0 × 10
11
 N/m
2
Q.14 For a given material, the Y oung’s modulus is 2.4 times that
of rigidity modulus. It’s poisson’s ratio is
(a) 1.2 (b) 1.02
(c) 0.2 (d)2
Q.15A wire of length 1m is stretched by a force of 10N. The
area of cross-section of the wire is 2 × 10
–6
 m
2
 and Y is
2 × 10
11
N/m
2
. Increase in length of the wire will be -
(a) 2.5 × 10
–5
 cm (b) 2.5 × 10
–5
 mm
(c) 2.5 × 10
–5
 m (d) None of these
Q.16 A stress of 1kg/mm
2
 is applied on a wire. If the modulus of
elasticity of the  wire is 10
10
 dyne/cm
2
, then the percentage
increase in the length of the wire will be
(a) 0.007 (b) 0.0098 (c) 98 (d) 9.8
Q.17A uniform steel wire of density 7800kg/m
3
 is 2.5 m long
and weighs 15.6 × 10
–3
 kg. It extends by 1.25 mm when
loaded by 8kg. Calculate the value of young’s modulus of
elasticity for steel.
(a) 1.96 × 10
11
 N/m
2
(b) 19.6 × 10
11
 N/m
2
(c) 196 × 10
11
 N/m
2
(d) None of these
Page 3


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 Length of a wire is doubled, when 20 × 10
8
 N/m
2
 stress is
applied on it. Its Y oung’s modulus of elasticity in N/m
2
 will
be
(a) 20 × 10
8
(b) 20 × 10
9
(c) 20 × 10
10
(d) 10 × 10
8
Q.2 A steel wire of uniform cross-sectional area 2mm
2
 is heated
upto 50°C and clamped rigidly at two ends. If the
temperature of wire falls to 30° then change in tension in
the wire will be, if coefficient of linear expansion of steel
is 1.1 × 10
–5
 /°C and young's modulus of elasticity of steel
is 2 × 10
11
 N/m
2
.
(a) 44 N (b) 88 N
(c) 132 N (d) 22 N
Q.3 The work done in increasing the length of a one metre long
wire of cross-sectional area 1mm
2
 through 1mm will be
(Y = 2 × 10
11
 N/m
2
)
(a) 250 J (b) 10 J
(c) 5 J (d) 0.1 J
Q.4 A spring is stretched by 3cm when a load of 5.4 × 10
6
 dyne
is suspended from it. Work done will be-
(a) 8.1 × 10
6
 J (b) 8 × 10
6
 J
(c) 8.0 × 10
6
 erg (d) 8.1 ×10
6
 erg
2
DPP/ P 20
Q.5 A wire of length 1m and area of cross section 4 × 10
-8
 m
2
increases in length by 0.2 cm when a force of 16 N is applied.
V alue of Y for the material of the wire will be
(a) 2 × 10
6
 N/m
2
(b) 2 × 10
11
 kg/m
2
(c) 2 × 10
11
 N/mm
2
(d) 2 × 10
11
 N/m
2
Q.6 The volume of a solid rubber ball when it is carried from the
surface to the bottom of a 200 m deep lake decreases by
0.1%. The value for bulk modulus of elasticity for rubber will
be
(a) 2 × 10
9
 Pa (b) 2 × 10
6
 Pa
(c) 2 × 10
4
 Pa (d) 2 × 10
–4
 Pa
Q.7 A steel wire is 4.0 m long and 2 mm in diameter. Young’s
modulus of steel is 1.96 × 10
11
 N/m
2
. If a mass of 20 kg is
suspended from it the elongation produced will be -
(a) 2 .5 4 m m (b) 1.27 mm
(c) 0.64 mm (d) 0.27 mm
Q.8 A brass rod is to support a load of 400 N. If its elastic limit is
4.0 × 10
8
 N/m
2
 its minimum diameter must be -
(a) 1.13 mm (b) 2.26 mm
(c) 3.71 mm (d) 4.52 mm
Q.9 A 4.0 m long copper wire of cross sectional area 1.2 cm
2
 is
stretched by a force of 4.8 × 10
3 
N stress will be -
(a) 4.0 × 10
7
 N/mm
2
(b) 4.0 × 10
7
 KN/m
2
(c) 4.0 × 10
7
 N/m
2
(d) None of these
Q.10 A copper rod 2m long is stretched by 1mm. Strain will be -
(a) 10
–4
, volumetric (b) 5 × 10
–4
, volumetric
(c) 5 × 10
–4
, longitudinal (d) 5 × 10
–3
, volumetric
Q.11 A wire of cross sectional area 3mm
2
 is just stretched between
two fixed points at a temperature of 20°C. Determine the
tension when the temperature falls to 20°C. Coefficient of
linear expansion a = 10
–5
 /°C and Y = 2 × 10
11
 N/m
2
.
(a) 120 KN (b) 20 N (c) 120 N (d) 102 N
Q.12 The compressibility of water is 5 × 10
–10
 m
2
/N. If it is
subjected to a pressure of 15 MPa, the fractional decrease in
volume will be -
(a) 3.3 × 10
–5
(b) 5.6 × 10
–4
(c) 7.5 × 10
–3
(d) 1.5 × 10
–2
Q.13 The Young’s modulus of steel is 2 × 10
11
 N/m
2
 and its
coefficient of linear expansion is 1.1 × 10
–5 
per deg. The
pressure  to be applied to the ends of a steel cylinder to
keep its length constant on raising its temperature by 100ºC,
will be -
(a) 5.5 × 10
4
 N/m
2
(b) 1.8 × 10
6
 N/m
2
(c) 2.2 × 10
8
 N/m
2
(d) 2.0 × 10
11
 N/m
2
Q.14 For a given material, the Y oung’s modulus is 2.4 times that
of rigidity modulus. It’s poisson’s ratio is
(a) 1.2 (b) 1.02
(c) 0.2 (d)2
Q.15A wire of length 1m is stretched by a force of 10N. The
area of cross-section of the wire is 2 × 10
–6
 m
2
 and Y is
2 × 10
11
N/m
2
. Increase in length of the wire will be -
(a) 2.5 × 10
–5
 cm (b) 2.5 × 10
–5
 mm
(c) 2.5 × 10
–5
 m (d) None of these
Q.16 A stress of 1kg/mm
2
 is applied on a wire. If the modulus of
elasticity of the  wire is 10
10
 dyne/cm
2
, then the percentage
increase in the length of the wire will be
(a) 0.007 (b) 0.0098 (c) 98 (d) 9.8
Q.17A uniform steel wire of density 7800kg/m
3
 is 2.5 m long
and weighs 15.6 × 10
–3
 kg. It extends by 1.25 mm when
loaded by 8kg. Calculate the value of young’s modulus of
elasticity for steel.
(a) 1.96 × 10
11
 N/m
2
(b) 19.6 × 10
11
 N/m
2
(c) 196 × 10
11
 N/m
2
(d) None of these
DPP/ P 20
3
Q.18 A metallic wire is suspended by suspending weight to it. If S
is longitudinal strain and Y its young's modulus of elasticity
then potential energy per unit volume will be
(a)
1
2
Y
2
S
2
(b)
1
2
Y
2
S
(c)
1
2
YS
2
(d) 2YS
2
Q.19 The lengths and radii of two wires of same material are
respectively L, 2L, and 2R, R. Equal weights are applied on
then. If the elongations produced in them are l
1
 and l
2
respectively then their ratio will be
(a) 2 : 1 (b) 4 : 1
(c) 8 : 1 (d) 1 : 8
Q.20 The ratio of radii of two wires of same material is 2 : 1. If
these wires are stretched by equal forces, then the ratio of
stresses produced in them will be
(a) 1 : 2 (b) 2 : 1
(c) 1 : 4 (d) 4 : 1
Q.21 A rod of length l and area of cross-section A is heated from
0°C to 100°C. The rod is so placed that it is not allowed to
increase in length, then the force developed is proportional to
(a) l (b) l 
–1
(c)A (d)A
–1
DIRECTIONS (Q.22-Q.24) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.22Mark the correct statements
(1) Sliding of molecular layer is much easier than
compression or expansion
(2) Reciprocal of bulk modulus of elasticity is called
compressibility
(3) Hollow shaft is much stronger than a solid rod of same
length and same mass
(4) It is difficult to twist a long rod as compared to small
rod
Q.23 Which statements are false for a metal?
(1) Y <h (2) Y =h
(3) Y 1/ <h (4) Y >h
Q.24 Which of the following relations are false
(1) ( ) 3Y K1 = -s (2) ( ) 6KY s = +h
(3)
9Y
K
Y
h
=
+h
(4)
0.5Y -h
s=
h
DIRECTIONS (Q.25-Q.27) : Read the passage given below and
answer the questions that follows :
A bar of cross section A is subjected to equal and opposite tensile
forces F at its ends. Consider a plane through the bar making an
angle q with a plane at right angles to the bar as shown in figure.
F
q
F
Q.25 The tensile stress at this plane in terms of F, A and q is
(a)
2
Fcos
A
q
(b)
2
F
A cos q
(c)
2
Fsin
A
q
(d)
2
F
A sin q
Q.26In the above problem, for what value of q is the tensile
stress maximum ?
(a) Zero (b) 90° (c) 45° (d) 30°
Page 4


DIRECTIONS (Q.1-Q.21) : There are 21 multiple choice questions.
Each question has 4 choices (a), (b), (c) and (d), out of which ONLY
ONE choice is correct.
Q.1 Length of a wire is doubled, when 20 × 10
8
 N/m
2
 stress is
applied on it. Its Y oung’s modulus of elasticity in N/m
2
 will
be
(a) 20 × 10
8
(b) 20 × 10
9
(c) 20 × 10
10
(d) 10 × 10
8
Q.2 A steel wire of uniform cross-sectional area 2mm
2
 is heated
upto 50°C and clamped rigidly at two ends. If the
temperature of wire falls to 30° then change in tension in
the wire will be, if coefficient of linear expansion of steel
is 1.1 × 10
–5
 /°C and young's modulus of elasticity of steel
is 2 × 10
11
 N/m
2
.
(a) 44 N (b) 88 N
(c) 132 N (d) 22 N
Q.3 The work done in increasing the length of a one metre long
wire of cross-sectional area 1mm
2
 through 1mm will be
(Y = 2 × 10
11
 N/m
2
)
(a) 250 J (b) 10 J
(c) 5 J (d) 0.1 J
Q.4 A spring is stretched by 3cm when a load of 5.4 × 10
6
 dyne
is suspended from it. Work done will be-
(a) 8.1 × 10
6
 J (b) 8 × 10
6
 J
(c) 8.0 × 10
6
 erg (d) 8.1 ×10
6
 erg
2
DPP/ P 20
Q.5 A wire of length 1m and area of cross section 4 × 10
-8
 m
2
increases in length by 0.2 cm when a force of 16 N is applied.
V alue of Y for the material of the wire will be
(a) 2 × 10
6
 N/m
2
(b) 2 × 10
11
 kg/m
2
(c) 2 × 10
11
 N/mm
2
(d) 2 × 10
11
 N/m
2
Q.6 The volume of a solid rubber ball when it is carried from the
surface to the bottom of a 200 m deep lake decreases by
0.1%. The value for bulk modulus of elasticity for rubber will
be
(a) 2 × 10
9
 Pa (b) 2 × 10
6
 Pa
(c) 2 × 10
4
 Pa (d) 2 × 10
–4
 Pa
Q.7 A steel wire is 4.0 m long and 2 mm in diameter. Young’s
modulus of steel is 1.96 × 10
11
 N/m
2
. If a mass of 20 kg is
suspended from it the elongation produced will be -
(a) 2 .5 4 m m (b) 1.27 mm
(c) 0.64 mm (d) 0.27 mm
Q.8 A brass rod is to support a load of 400 N. If its elastic limit is
4.0 × 10
8
 N/m
2
 its minimum diameter must be -
(a) 1.13 mm (b) 2.26 mm
(c) 3.71 mm (d) 4.52 mm
Q.9 A 4.0 m long copper wire of cross sectional area 1.2 cm
2
 is
stretched by a force of 4.8 × 10
3 
N stress will be -
(a) 4.0 × 10
7
 N/mm
2
(b) 4.0 × 10
7
 KN/m
2
(c) 4.0 × 10
7
 N/m
2
(d) None of these
Q.10 A copper rod 2m long is stretched by 1mm. Strain will be -
(a) 10
–4
, volumetric (b) 5 × 10
–4
, volumetric
(c) 5 × 10
–4
, longitudinal (d) 5 × 10
–3
, volumetric
Q.11 A wire of cross sectional area 3mm
2
 is just stretched between
two fixed points at a temperature of 20°C. Determine the
tension when the temperature falls to 20°C. Coefficient of
linear expansion a = 10
–5
 /°C and Y = 2 × 10
11
 N/m
2
.
(a) 120 KN (b) 20 N (c) 120 N (d) 102 N
Q.12 The compressibility of water is 5 × 10
–10
 m
2
/N. If it is
subjected to a pressure of 15 MPa, the fractional decrease in
volume will be -
(a) 3.3 × 10
–5
(b) 5.6 × 10
–4
(c) 7.5 × 10
–3
(d) 1.5 × 10
–2
Q.13 The Young’s modulus of steel is 2 × 10
11
 N/m
2
 and its
coefficient of linear expansion is 1.1 × 10
–5 
per deg. The
pressure  to be applied to the ends of a steel cylinder to
keep its length constant on raising its temperature by 100ºC,
will be -
(a) 5.5 × 10
4
 N/m
2
(b) 1.8 × 10
6
 N/m
2
(c) 2.2 × 10
8
 N/m
2
(d) 2.0 × 10
11
 N/m
2
Q.14 For a given material, the Y oung’s modulus is 2.4 times that
of rigidity modulus. It’s poisson’s ratio is
(a) 1.2 (b) 1.02
(c) 0.2 (d)2
Q.15A wire of length 1m is stretched by a force of 10N. The
area of cross-section of the wire is 2 × 10
–6
 m
2
 and Y is
2 × 10
11
N/m
2
. Increase in length of the wire will be -
(a) 2.5 × 10
–5
 cm (b) 2.5 × 10
–5
 mm
(c) 2.5 × 10
–5
 m (d) None of these
Q.16 A stress of 1kg/mm
2
 is applied on a wire. If the modulus of
elasticity of the  wire is 10
10
 dyne/cm
2
, then the percentage
increase in the length of the wire will be
(a) 0.007 (b) 0.0098 (c) 98 (d) 9.8
Q.17A uniform steel wire of density 7800kg/m
3
 is 2.5 m long
and weighs 15.6 × 10
–3
 kg. It extends by 1.25 mm when
loaded by 8kg. Calculate the value of young’s modulus of
elasticity for steel.
(a) 1.96 × 10
11
 N/m
2
(b) 19.6 × 10
11
 N/m
2
(c) 196 × 10
11
 N/m
2
(d) None of these
DPP/ P 20
3
Q.18 A metallic wire is suspended by suspending weight to it. If S
is longitudinal strain and Y its young's modulus of elasticity
then potential energy per unit volume will be
(a)
1
2
Y
2
S
2
(b)
1
2
Y
2
S
(c)
1
2
YS
2
(d) 2YS
2
Q.19 The lengths and radii of two wires of same material are
respectively L, 2L, and 2R, R. Equal weights are applied on
then. If the elongations produced in them are l
1
 and l
2
respectively then their ratio will be
(a) 2 : 1 (b) 4 : 1
(c) 8 : 1 (d) 1 : 8
Q.20 The ratio of radii of two wires of same material is 2 : 1. If
these wires are stretched by equal forces, then the ratio of
stresses produced in them will be
(a) 1 : 2 (b) 2 : 1
(c) 1 : 4 (d) 4 : 1
Q.21 A rod of length l and area of cross-section A is heated from
0°C to 100°C. The rod is so placed that it is not allowed to
increase in length, then the force developed is proportional to
(a) l (b) l 
–1
(c)A (d)A
–1
DIRECTIONS (Q.22-Q.24) : In the following questions,
more than one of the answers  given are correct. Select the
correct answers and mark it according to the following
codes:
Codes :
(a) 1, 2 and 3 are correct (b) 1 and 2 are correct
(c) 2 and 4 are correct (d) 1 and 3 are correct
Q.22Mark the correct statements
(1) Sliding of molecular layer is much easier than
compression or expansion
(2) Reciprocal of bulk modulus of elasticity is called
compressibility
(3) Hollow shaft is much stronger than a solid rod of same
length and same mass
(4) It is difficult to twist a long rod as compared to small
rod
Q.23 Which statements are false for a metal?
(1) Y <h (2) Y =h
(3) Y 1/ <h (4) Y >h
Q.24 Which of the following relations are false
(1) ( ) 3Y K1 = -s (2) ( ) 6KY s = +h
(3)
9Y
K
Y
h
=
+h
(4)
0.5Y -h
s=
h
DIRECTIONS (Q.25-Q.27) : Read the passage given below and
answer the questions that follows :
A bar of cross section A is subjected to equal and opposite tensile
forces F at its ends. Consider a plane through the bar making an
angle q with a plane at right angles to the bar as shown in figure.
F
q
F
Q.25 The tensile stress at this plane in terms of F, A and q is
(a)
2
Fcos
A
q
(b)
2
F
A cos q
(c)
2
Fsin
A
q
(d)
2
F
A sin q
Q.26In the above problem, for what value of q is the tensile
stress maximum ?
(a) Zero (b) 90° (c) 45° (d) 30°
4
DPP/ P 20
Q.27 The shearing stress at the plane, in terms of F, A and q is
(a)
Fcos2
2A
q
(b)
Fsin2
2A
q
(c)
Fsin
A
q
(d)
F cos
A
q
DIRECTIONS (Qs. 28-Q.30) : Each of these questions contains two
statements: Statement-1 (Assertion) and Statement-2 (Reason). Each
of these questions has four alternative choices, only one of which is
the correct answer. You have to select the correct choice.
(a) Statement-1 is True, Statement-2 is True; Statement-2 is a
correct explanation for  Statement-1.
(b) Statement-1 is True, Statement-2 is True; Statement-2 is
NOT a correct explanation for Statement-1.
(c) Statement -1 is False, Statement-2 is True.
(d) Statement -1 is True, Statement-2 is False.
Q.28Statement -1 : Steel is more elastic than rubber.
Statement -2 : Under given deforming force, steel is
deformed less than rubber.
Q.29Statement -1 : Bulk modulus of elasticity (K) represents
incompressibility of the material.
Statement -2 : Bulk modulus of elasticity is proportional
to change in pressure.
Q.30 Statement -1 :The bridges declared unsafe after a long use.
Statement -2 : Elastic strength of bridges losses with time.