Diploma in Engineering (Lateral) III (Third) Semester Examination 2011-12
Course Code: DIPL303 Paper ID: 0743103
Applied Mechanics
Time: 3 Hours Max. Marks: 60 Max Marks: 75
Note: Attempt six questions in all. Q. No. 1 is compulsory.
1. Answer any five of the following (limit your answer to 50 words). (3x5=15)
a) Define Hook’s law with the help of diagram.
b) Define angle of friction and coefficient of friction.
c) Determine the magnitude and direction of the resultant of the following set of forces acting on a body:
i) 200 N inclined 30o with east towards north.
ii) 250 N towards the north.
iii) 300 N towards North West, and
iv) 350 N inclined at 40o with west towards south.
d) Define and differentiate between perfect, deficient and redundant truss.
e) A steel tie rod 50 mm in diameter and 2.5 m long is subjected to a pull of 10kN Calculate the percentage change in extension produced under the same pull by boring the rod centrally for 1.2 m length; the bore being 25 mm in diameter. For steel modulus of elasticity is 2* 105 N/mm2.
f) The resultant of two forces P and Q is at right angle to P. Show that the angle between the forces is cos – (-P/Q).
g) Determine the reactions at A and B for the beam loaded as shown in Fig.1.
h) An alloy specimen has a modulus of elasticity of 120 GPa and modulus of rigidity of 45 GPa. Determine the Poisson’s ratio of the material.
2. An inclined truss shown in Fig. 2 is loaded as shown. Determine the nature and magnitude of the forces in the members BC, GC and GF of the truss. (9)
3. A plate measuring 6 m x 4 m is acted upon a set of forces in its plane as depicted in Fig.3. Determine the magnitude, direction and position of the resultant force. (9)
4. State and explain laws of sliding friction. (9)
5. A body resting on a rough horizontal plane required a pull of 24 N inclined at 30o to the plane just to move it. It was also found that a push of 30 N at 30o to the plane was just enough to cause motion to impend. Make calculations for the weight of body and the coefficient of friction. (9)
6. Explain the triangle law and parallelogram law of forces with the help of diagram. (9)
7. A beam weighing 450 N is held in a horizontal position by three vertical wires, one attached to each end of the beam, one to the middle of its length. The outer wires of brass off diameter 1.25 mm and the central wire each of steel of diameter 0.625 mm. If the beam is rigid and wires of the same length and unstressed before the beam is attached, estimate the stresses wires of the same length and unstressed before the beam is attached, estimate the stresse. (9)
8. For a given material, young’s modulus is 110 GN/m2 and shear modulus is 42 GN/m2. Find the bulk modulus and lateral contraction of a round bar of 37.5 mm diameter and 2.4 m length when stretched 2.5 mm. (9)
Fig. 1
Fig.2
Fig.3