**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 2×10^{8} N/m^{2}, 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 5×10^{3}kg/m^{3}) (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 10^{11} N/m^{2} . 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) 3.18X10^{8}Pa (b)1.59mm (c) 2.5×10^{5}j/m^{3 } (d)7.92 J . 11.- infinity 12.- 0.5 13.- Y^{-1} .