Physics Classes

Tag: Mechanical properties of solids

  • Objective questions of mechanical properties of solids

    Objective questions of mechanical properties of solids

    This is the assignment for the practice of objective questions of mechanical properties of solids. Students can consider it as a test paper of the chapter mechanical properties of solids.

    1. Breaking stress depends on  (a) length of wire (b) Area of cross-section of wire (c) both a and b (d) independent of length and area of cross-section.

    2.Which of the following is perfectly plastic? (a) plasticine (b) Quartz fibre (c) steel (d) Rubber.

    3. the length of an elastic string is X meter when the tension is 8N and Y m when tension is 10N , what will be the length when tension is 18N .  (a) 4X-5Y    (b) 5Y-4X  (c)  9X-4Y (d)    4Y-9X.

    4. When a load of 10kg is hung in the wire, then extension of 2m is produced. Then work done by the restoring force is (a)200J (b) 100J (c) 50J (d) 25J  .

    5.Substance which can be elastically stretched to large value of strain is called (a) isomers (b) isodiapheres (c) Plastomers  (d) Elastomers .

    6. A force F doubles the length of the wire of cross-section a . Then the Young’s modulus of the wire is (a) F/a (b) F/3a (c) F/2a  (d) F/4a .

    7. Breaking stress of a material is 2×108 N/m2, what maximum length of the wire of this material can be taken so that the wire doesn’t break by own weight? ( density of material is 5×103kg/m3) (a) 1km (b)2km (c) 3km (d) 4km.

    8.Young modulus of elasticity for a gas is (a) 1 (b) infinity (c) zero (d) none of these .

    9. If we added an impurity in the material then its elasticity (a) may change (b) never change (c) remain the same (d) change by a factor of 5 .

    10. A structural steel rod has a  radius r = 10mm when a force 100 kN is applied . it stretches along its length Y for steel is 2x 1011 N/m2 . aswer the following questions-

     (i) what is the stress produced ?

     (ii)what is the elongation produced ?

    (iii) what is the elastic energy density of the steel rod ?

     (iv) elastic potential energy stored in the rod is what?

    11.Elasticity of a rigid body is ………..

    12. If Young’s modulus is three times of modulus of rigidity. Then the Poisson’s  ratio is equal to …………

    13. In case of bending of a beam , depression depends on the Young’s modulus  Y as proportional to …….

    14.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?

    Answers-

    1.-d      2.-a   3.-b    4.-b    5.-d     6.-a     7.-d     8.-c     9.-a    10.- (a) 3.18X108Pa  (b)1.59mm (c) 2.5×105j/m3  (d)7.92 J . 11.- infinity  12.- 0.5   13.-  Y-1 .

  • Important questions of elasticity

    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 1011N/m2  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 1010 N/m2.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-1/4th 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. [1010 dynes /cm2]