PH8151 Engineering Physics Chapter 1

1.14. EXERCISES

1.11A circular and a square cantilevers
are made of a same material and have equal
areas of cross-section and lengths. Find the
ratio of their depressions for a given load [ 6 ].

1.12A brass bar having 1 cm square cross-
sectional area is supported on two knife
edges 1 m apart. A load of 1 kg at the
centre of the bar depresses the midpoint by

2.51 mm. What is the Young’s Modulus of

brass?

1.13A disc of 10 cm radius and mass 1 kg is

suspended in a horizontal plane by a vertical

wire attached to its centre. If the diameter

of the wire is 1 mm, its length is 1.5 metres,

and the period of torsional vibration of the

disc is 5 secs, find the Rigidity Modulus of

the wire.

Answers:

1.1 (D) 2000 N

1.2 (A) material of the wire

1.3 (B) 20 kg

1.4(A) 1/8

1.5 (B) 1.0 mm

1.6 (A) smallest at the top and gradually
increases down the rod

1.7 (A)l/l

1.8 (C)l^1 TT^22 ≠≠Tl^21 T^1

1.9 (B) when the mass is at the lowest

point

1.10 135 mm

1.11^3 fi

1.12 97 .7GPa

1.13 120 .6GPA

Anna University Semester End Examination Questions

Part A (2 marks) - Questions for Short Answers (3 to 3.5 minutes to answer each)

1. Although both pressure and stress are measured in pascal (Pa), physically they
   are dierent. Explain how do they dier from each other.


2. Which is more elastic; rubber or steel? Explain your answer.


3. State Hooke’s law of elasticity and define elastic modulus.


4. For small deformations the ratio stress/strain remains constant for a material
   such as steel. What happens to this ratio as the deformation is made larges
   and larger?


5. An steel wire is cut into half of its original length. Does this change the
   maximum tensile load the wire can support? Explain your answer.


6. Draw the typical stress- strain diagram and label its dierent regions, for a
   material such as steel.

PH8151 43 LICET