A wire suspended vertically from one of its ends is stretched by attaching a weight of 200 N 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

Question-2

Two rods of different materials having coefficients of linear expansion α_{1 }and α_{2} , Young's modulii Y_{1} and Y_{2 }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 α_{1} : α_{2} =2 : 3, the thermal stresses developed in the two rods are equal provided Y_{1} : Y_{2} is equal to :

(A)

2 : 3

(B)

1 : 1

(C)

3 : 2

(D)

4 : 9

Question-3

If S is stress and Y is young's modulus of material of a wire, the energy stored in the wire per unit volume is :

(A)

2Y / S

(B)

S / 2Y

(C)

2 S^{2} Y

(D)

Question-4

The upper end of a wire, 1 m long and 4 mm radius, is clamped. The lower end is twisted by an angle of 30^{o}. The angle of shear at the surface is :

(A)

12^{o}

(B)

1.2^{o}

(C)

0.12^{o}

(D)

0.012^{o}

Question-5

The Poisson's ratio for a material is 0.1. If the longitudinal strain of a rod of this material is 1 x 10^{-3}, then the percentage change in the volume of rod will be :

(A)8%

(B)0.8%

(C)0.08%

(D)0.008%

Question-6

A thick copper rope of density 1.2 X 10^{3 }kg m ^{-3 }and Young's modulus 5 X 10^{6} N m^{-2}. 8 m in length,when hung from the ceiling of a room, the increase in its length due to its own weight is:

(A)

9.6 X 10^{-5}m

(B)

19.2 X 10^{-7}m

(C)

9.6 X 10^{-2}m

(D)

9.6 m

Question-7

A substance breaks down by a stress of 10^{6} N / m ^{2}. If the density of the material of the wire is 3 X 10^{3} kg / m ^{3}, then the length of the wire of the substance which will break under its own weight when suspended vertically will be :

(A)

66.6 m

(B)

60.0 m

(C)

33.3 mm

(D)

30.3 mm

Question-8

The potential energy function for the force between two atoms in a diatomic molecule is approximately given by.

where a and b are constants and x is the distance between the atoms. If the dissociation energy of the molecule is D = [U (x = ∞) - U _{at equilibrium I D is.}

(A)

(B)

(C)

(D)

Question-9

For a constant hydraulic stress on an object, the fractional change in the object's volume ( Δ V / V ) and its bulk modulus (B) are related as:

(A)

(B)

(C)

(D)

Question-10

A body of weight mg is hanging on a string which extends in length by l. The work done in extending the string is :

(A)

mgl

(B)

mgl / 2

(C)

2 mgl

(D)

mg

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