ELASTICITY

1 Hooke’s law essentially defines :
a) stress b) Strain c) Yield point d) Elastic limit
2 The beams of metal supported at the two ends is loaded at the centre . The depression at the centre
is proportionnal to : a) Y2 b) Y c) 1/Y d) 1/Y2
3 Bulk modulus was first defined by : a) Young b) Bulk c) None d) Maxwell
4 On stretching a wire, the elastic energy stored per unit volume is:
a) Fdl /2Al b) FA/ 2l c) Fl/ 2A d) Fl/2
5 The Young’s modulus of a wire of length L and radius r is Y newton per square metre. If the lengthm
is reduced to L /2 and radius r/2, its Young’s modulus will be : a) Y/2 b) Y c) 2Y d) 4Y
6 The work done per unit volume in stretching the wire is equale to :
a) Stress X Strain b) (1/2) Stress X Strain c) Stress / Strain d) Strain / Stress
7 The relationship between Y, h and s is :
a) Y = 2h ( 1 + s ) b) h = 2Y (1+ s ) c) s = 2Y/ ( 1 + h ) d) Y = h( 1+ s )
8 A wire is stretched by 0.01 m by a certian force F. Another wire of same material whose diameter
and lengths are double to the original wire is stretched by the same force. Then its elongation
will be : a) 0.005m b) 0.01m c) 0.02m d) 0.02m
9 An iron bar of length l and having cross section A is heated from 00C to 1000C. If this bar is held so
that it is not permited to expand or bend , the gigantic force that it developed is :
a) Directly propotional to the length of the bar b) Inversly propotional to the length of the bar
c) Indipendent of the length of bar d) Inversly propotional to the cross-section of the bar
10 When a body undergoes a linear tensile strain it experiences a lateral contraction also. The ratio of
lateral strain to longitudinal strain is known as :
a) Young’s modulus b) Bulk modulus c) Poisson’s ratio d) Hook’s law
11 Two rods of different materials having coefficients of linear expantion a1 ,a2 and Young’s modulii
Y1and Y2 respectively are fixed between two rigid massive walls. The rods are heated such that they
undergo the same increase in temperature . There is no bending of rods. If a1 : a2 = 2 :3, the thermal
stresses developed in the two rods are equal provided Y1 : Y2 is equal to :
a) 2 : 3 b) 1 : 1 c) 3 : 2 d) 4 : 9
12 The breaking stress for a wire of unit cross section is called its :
a)Yield point b) Tensile strength c) Elastic fatigue d) Young;s modulus
13 Two wires A and B are of the same material. Their lengths are in the ratio 1 :2 and the diameters are
in the ratio 2 : 1. If they are pulled by the same force , the increase in length will be in the ratio:
a) 2 :1 b) 1 : 4 c) 1 : 8 d) 8 : 1
14 The following four wires length L and radius r are made of the same material . Which of these will
have the largest extension when the same tension is applied ? a) L =50cm , r = 0.25mm
b)L = 100cm , r = 0.5mm c) L = 200cm , r = 1mm d) L = 300cm, r = 15mm
15 A cylinder fixed rigidly at one end has a tangential force applied to its other end. The shape and
volume of the cylinder remain unaltered . The strain produced in the cylinder is :
a) Longitudinal b) Volumetric c) Shear d) Zero
16 A metal bar of length L, area of cross-section A, Young’s modulus Y and coefficient of linear
expansion a is clamped between two stout pillars . Now it is heated throgh t0 c. The force exerted by
the bar is : a) YA at b) YALt c) YA a Lt d) Ya Lt /A
17 For steel Y=2 X1011 N/m2. The force required to double the length of a steel wire of area 1cm2 is :
a) 2 X 107N b) 2 X106 N c)2 X108N d) 2 X 105N