**This assignment contain Important questions of elasticity **

( Mechanical properties of solids)

1. what is more elastic water or air?

2. Write copper,steel,rubber and glass in the increasing order of their elasticity.

3.How do modulus of elasticity of a material changes with temperature?

4. The breaking force for a wire is F, what will be the breaking force (i) two parallel wire of same size? (ii) for a single wire of double of thickness? Ans- 2F and 4F

5.What is the modulus of rigidity of a fluid ? Ans-0

6.Define Young’s modulus and modulus of rigidity. Give their expression and units.

7. What is the meant by elastic limit and angle of share?

8. Define Poisson’s ratio, what is its value for perfectly incompressible substance? Ans-0.5

9. Derive an expression for the elastic potential energy of a wire under stress.

10. What is the role of elasticity in everyday life? Give two example.

11. A 4m long aluminium wire whose diameter is 3 mm is used to support a mass of 50 kg. What will be the elongation of the wire? Y for aluminium is 7 x 10^{11}N/m^{2} ans-3.9mm

12-Calculate the percentage increase in the length of a wire of diameter 2.5mm stretched by a force of 100kg-wt Young’s modulus of the wire is 12.5 x 10^{10} N/m^{2}.ans-0.16

13.Acable is replaced by anther cable of same length and material but twice the diameter (a) How will this effect the elongation under given load? (b)How does this effect the maximum load it can support without exceeding the elastic limit? Ans-1/4^{th} and D ^{2} .

14. A material has poisson’s ratio 0.5. If a uniform rod of it suffers a longitudinal strain of 2 x 10^{-3} . What is the percentage increase in its volume? Ans-0%

15.Two wires of different materials are suspended from a rigid support. They have the same length and diameter carrying the same load at their free ends . (a) Will the stress and strain in each wire be the same? (b) will the extension in both wire will be same? Ans- (a) stress same strain different (b) different.

16.The stress strain graph for two materials A and B are shown in fig.

(a) Which one has greater Young’s modulus ?(b) which one is strongest material?(c) which is more ductile?(d) which is more brittle?

17. A wire stretches a certain amount under a load. If the load and diameter are both increased to three times, find the stretch cause in the wire.

Ans. [3/4l]

18.A metal bar of length L and area of the cross-section A is rigidly clamped between two walls. The young’s modulus of its material is Y and the coefficient of linear expansion is. α. The bar is heated so that its temperature is increased by C. find the force exerted at the ends of. the bar.

Ans. [YA α]

19.A metallic wire is suspended by attaching some weight to it. If is the longitudinal strain and Y is young’s modulus, find the ratio between elastic potential energy and the energy density.

Ans. [volume]

20.A spherical ball contracts in volume by 0.01 when subjected to a normal pressure of 100 atmospheres. What is the bulk modulus of its material in cgs units?

Ans. [10^{10} dynes /cm^{2}]