JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ELEMENTS OF MECHANICAL ENGINEERING Previous Question Paper (September/October - 2023 - R13)
Question paper consists of Part A and Part B. Part A is compulsory (25 marks). Part B: Answer any one question from each unit (50 marks).
Part A
Define the term Poisson’s ratio. What is its maximum value?
Answer
Poisson’s ratio is defined as the ratio of lateral strain to longitudinal strain within the elastic limit when a material is subjected to a uniaxial stress. It is denoted by the Greek letter ν or μ.
The theoretical maximum value of Poisson's ratio for an isotropic material is 0.5, which corresponds to a perfectly incompressible material.
In a composite bar, bars having same cross-sectional area, one bar shares one-third of the total load. What is the ratio of their Young’s modulus (E1/E2)?
Answer
For a composite bar where the bars are subjected to the same strain (assuming parallel arrangement), the load shared by each bar is proportional to the product of its Young's modulus and cross-sectional area. Given that the cross-sectional areas are equal (A1 = A2 = A), the load P shared by each bar is P = E × A × ε. Since the total load P_total = P1 + P2, and bar 1 carries one-third of the total load (P1 = 1/3 P_total), it follows that P2 = 2/3 P_total.
Substituting the load values:
Thus, the ratio of their Young's moduli E1/E2 is 0.5.
What is the importance of drawing shear force and bending moment diagrams?
Answer
Sign in to view the complete answer paper.
State the assumptions made in deriving the bending equation.
Answer
Sign in to view the complete answer paper.
Differentiate between thin and thick cylinders.
Answer
Sign in to view the complete answer paper.
Write Lame’s equation for stress in thick cylinder. How it is used in the analyses of stresses in thick cylinder?
Answer
Sign in to view the complete answer paper.
Classify IC engines on the basis of cycle of operation and type of fuel.
Answer
Sign in to view the complete answer paper.
List advantages of internal combustion engine over external combustion engine.
Answer
Sign in to view the complete answer paper.
State the law of belting.
Answer
Sign in to view the complete answer paper.
What is the effect of centre distance variation on speed ratio in gears?
Answer
Sign in to view the complete answer paper.
Part B
A copper rod of diameter 20 mm is enclosed within a steel tube of 30 mm internal diameter and thickness 2 mm. The assembly is attached to rigid plates at both the ends and is subjected to a tensile load of 30 kN. Find the stresses in the rod and the tube if Young’s modulus, E = 200 GPa for steel and 120 GPa for copper. Also find the strain and the deformation in each member.
Answer
Sign in to view the complete answer paper.
Derive relationship between Young’s modulus (E) and Bulk modulus (K).
Answer
Sign in to view the complete answer paper.
A steel bar of square section 30 × 30 mm and a length of 600 mm is subjected to an axial tensile force of 150 kN. Determine the changes in dimensions of the bar if Young’s modulus, E = 200 GPa and Poisson’s ratio, v = 0.3.
Answer
Sign in to view the complete answer paper.
A simply supported beam of span 6 m is carrying an uniformly distributed load of 2 kN/m over the entire span. Calculate the magnitude of shear force and bending moment at every section of 2 m from the left support. Also, draw the shear force and bending moment diagrams.
Answer
Sign in to view the complete answer paper.
A beam of rectangular cross section 50 mm wide and 150 mm deep is used as a cantilever 6 m long and subjected to a uniformly distributed load of 2 N/m over the centre length. Determine the bending stress at 50 mm from the top fibre, at the mid-span of the beam. Also, calculate the maximum bending stress.
Answer
Sign in to view the complete answer paper.
A thin cylindrical shell made of 4-mm-thick copper plate is filled with oil under a pressure of 3 MPa. The internal diameter of the cylinder is 200 mm and its length is 800 mm. Determine the additional volume of oil pumped inside the cylinder so to develop the required pressure. Given E for copper = 104 GPa, ν for copper = 0.32, and Bulk modulus of liquid K for oil = 2,800 MPa.
Answer
Sign in to view the complete answer paper.
What is the effective length of a column? How the end conditions affect the effective length? Consider at least three cases.
Answer
Sign in to view the complete answer paper.
The allowable maximum stress in a thick cylinder of radii 100 mm and 150 mm is 25 MPa. If the external pressure is zero what internal pressure can be applied?
Answer
Sign in to view the complete answer paper.
With neat sketches explain the working of four-stroke CI engine.
Answer
Sign in to view the complete answer paper.
Discuss the merits and demerits of four-stroke engines over two-stroke engines.
Answer
Sign in to view the complete answer paper.
Differentiate among mechanical efficiency, Volumetric efficiency, thermal efficiency and relative efficiency.
Answer
Sign in to view the complete answer paper.
The mechanical efficiency of a single cylinder four-stroke engine is 80%. The friction power is estimated to be 20 kW. Calculate the indicated power and brake power developed by the engine.
Answer
Sign in to view the complete answer paper.
Derive the expression for ratio of tensions in a belt drive.
Answer
Sign in to view the complete answer paper.
Two pulleys of diameters 500 mm and 300 mm are connected by a belt having tensions 3 kN and 2 kN on the two sides of the belt connecting them. If the power transmitted is 25 kW, find the speed of the belt.
Answer
Sign in to view the complete answer paper.
Explain with a neat sketch the 'sun and planet wheel'.
Answer
Sign in to view the complete answer paper.
In an epicyclic gear train, an arm carries two gears 1 and 2 having 40 and 50 teeth respectively. The arm rotates at 160 rpm ccw about the centre of gear 1, which is fixed. Determine the speed of the gear 2.
Answer
Sign in to view the complete answer paper.