PH8151 Engineering Physics Chapter 1

44 CHAPTER 1. PROPERTIES OF MATTER

7. Draw a representative stress-strain diagram of a brittle material.


8. Draw a representative stress-strain diagram of a ductile material.


9. List a set of information about a material that you can extract its stress-strain
   diagram.


10. Define Young’s Modulus. What is its unit?


11. Define Rigidity Modulus. What is its unit?


12. Define Bulk Modulus. What is its unit?


13. Define Poisson’s ratio.


14. When a compressed string is dissolved in acid what happens to the elastic
    potential energy of the string [ 8 ]?


15. When a wire is repeatedly bent back and forth it becomes hot. Why?


16. When a block of mass is suspended by a long wire of lengthL, the elastic
    potential energy stored in the wire is^12 ◊stress◊strain◊volume. Show that
    it is equal to^12 Mgl, wherelis the extension. The loss in gravitational potential
    energy of mass-earth system isMgl. Where does the remaining^12 Mglgo [ 8 ]?


17. List the factors that aect elastic modulus and tensile strength of materials.


18. How do temperature changes and presence of impurities aect elastic properties
    of materials?


19. How do hammering and rolling aect elastic properties of materials?


20. What is meant by (a) neutral surface and (b) neutral axis of a beam.


21. How are the various filaments of a beam aected when the beam is loaded?


22. Distinguish between uniform bending and non-uniform bending.


23. What are I- shape girders?


24. State the advantages and limitations of I-shaped girders.

Part B (16 marks) - Questions for detailed Answers (25 to 28 minutes to answer each)

1. Derive an expression for the torsional couple per unit angular twist when a
   cylinder is twisted.


2. Derive an expression for the period of oscillation of a torsional pendulum. How
   can it be used to determine the torsional rigidity (Rigidity Modulus) of a wire?


3. What is meant by bending moment of a beam? Derive the expression for the
   bending moment of a beam.


4. Derive the expression for the depression at the free end of a cantilever due
   to load. Describe an experiment to determine the young’s modulus of the
   cantilever using this expression.


5. Explain, with necessary theory, the method of determination of young’s mod-
   ulus of elasticity of the material of a beam supported at its ends and loaded in
   the middle (non-uniform bending).


6. Explain, with necessary theory, the method of determination of young’s mod-
   ulus of elasticity of the material of a beam supported symmetrically on two
   knife edges and loaded equally at its ends (uniform bending).

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