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Mechanical Engineering
1. In a crank and slotted lever quick-return motion, the distance between the fixed centres is 150 mm and the length of the driving crank is 75 mm. The ratio of the time taken on the cutting and
return strokes is
(a) 1.5
(b) 2.0
(c) 2.2
(d) 2.93
2. Which one of the following mechanisms is an inversion of double slider-crank chain?
(a) Elliptic trammels
(b) Beam engine
(c) Oscillating cylinder, engine
(d) Coupling rod of a locomotive
3. A slider moves with uniform velocity v on a revolving link of length r with angular velocity w. The Coriolis acceleration component of a point on the slider relative to a coincident point on the link is equal to
(a) w u parallel to the link
(b) 2w v perpendicular to the link
(c) wv perpendicular to the link
(d) 2w v parallel to the link
4. Which of the following statements are correct for mating gears with involute profiles?
1. The pressure angle, from the start of the engagement to the end of the engagement,remains constant.
2. The pressure angle is maximum at the beginning of the engagement, reduces to zero at pitch point, starts decreasing and again becomes maximum at the end of the engagement.
3. The face and flank of the teeth are generated by a single curve and the normal to this curve at any point is tangent to the base circle of the gear.
4. The centre distance for a pair of mating gears can be varied within limits without altering the velocity ratio.
Select the correct answer using the code given below.
(a) 1, 3 and 4
(b) 1 and 3 only
(c) 2 and 4 only
(d) 2, 3 and 4
5. Two involute gears are designed to mesh for a given centre distance and a given angular velocity ratio (other than 1). During assembly, the centre distance has increased slightly. Then which of the following changes occur?
1. Velocity ratio changes
2. Pressure angle changes
3. Pitch circle diameter changes
4. Working depth changes
5. Base circle radius changes
Select the correct answer using the code given below.
(a) 1, 2 and 3
(b) 2, 3 and 4
(c) 2 and 5
(d) 3 and 5
6. In a governor, if the equilibrium speed is constant for all radii of rotation of balls, the governor is said to be
(a) stable
(b) unstable
(c) inertial
(d) isochronous
7. Critical speed is expressed as
(a) rotation of shaft in degrees
(b) rotation of shaft in radians
(c) rotation of shaft in minutes
(d) natural frequency of the shaft
8. In a locomotive, the ratio of the connecting rod length to the crank radius is kept very large in order to
(a) minimize the effect of primary forces
(b) minimize the effect of secondary forces
(c) have perfect balancing
(d) start the locomotive conveniently
9. In balancing of single-cylinder engine, the rotating unbalance is
(a) completely made zero and so also the reciprocating unbalance
(b) completely made zero and the reciprocating unbalance is partially reduced
(c) partially reduced and the reciprocating unbalance is completely made zero
(d) partially reduced and so also the reciprocating unbalance
10. The first critical speed of an automobile running on a sinusoidal road is calculated by (modelling it as a single degree of freedom system)
(a) resonance
(b) approximation
(c) superposition principle
(d) Rayleigh quotient
11. Linear vibration analysis has the greatest advantage because of
(a) Newton's laws of motion
(b) eigenvalue analysis
(c) Rayleigh quotient
(d) principle of superposition
12. Which of the following are responsible for occurrence of critical or whirling speed of shaft?
1. Eccentric mounting of the rotor
2. Non-uniform distribution of rotor material
3. Bending of shaft due to the weight of the rotor and the shaft itself
4. Environmental effect such as effect of moisture and temperature
Select the correct answer using the code given below.
(a) 1, 2, 3and4
(b) 1, 2and3only
(c) 1, 2 and 4 only
(d) 1 and 3 only
13. If a rectangular key of 8 mm width and 6 mm height and a shaft of diameter 32 mm are made of same material, then the necessary length of the key for equal shear strength of shaft and key. will be (neglecting stress concentration on the shaft)
(a) 50.24 mm
(b) 55 mm
(c) 45 mm
(d) 60.24 mm
14. Rivets undergo single shear in
(a) lap joint and single-cover butt joint
(b) single-cover butt joint and double-cover butt joint
(c) lap joint and double-cover butt joint
(d) lap joint only
15. A multi-disc clutch employs 3 steel and 2 bronze discs having outer diameter of 300 mm and inner diameter of 175 mm. If the coefficient of friction is 0.25 and axial force on each pair of surfaces is 5 kN, then the torque transmitted (assuming uniform wear) is
(a) 416.6 N m
(b) 887.5 N m
(c) 1093.75 N m
(d) 593.75 N m
16. Which of the following statements are correct regarding power transmission through V-belts?
1. V-belts are used at the high-speed end.
2. V-belts are used at the low-speed end.
3. V-belts are of standard lengths.
4. V-angles of pulleys and belts are standardized.
Select the correct answer using the code given below.
(a) 1 and 3 only
(b) 2 and 4 only
(c) 2, 3and 4
(d) 1, 3and 4
17. Pressure angle of involute gears does not exceed 25°, since
(a) this will lead to unwanted radial force
(b) the number of teeth to avoid undercutting will be very high
(c) no cutters are available
(d) gears will become too small
18. Consider the following statements :
In the case of involute gears in contact
1. the motion is one of pure rolling
2. pressure angle does not change during contact
3. velocity ratio does not change
4. output torque of the driven gear changes
Which of the above statements are correct?
(a) 1 and 2
(b) 2and4
(c) 2 and 3
(d) 3 and 4
19. If the centre distance between a pair of spur gears in mesh is 240 mm and the pinion moves five times faster than the gear, then the pitch circle diameters of pinion and gear respectively are
(a) 40 mm and 200 mm
(b) 80 mm and 400 mm
(c) 60 mm and 300 mm
(d) 50 mm and 250 mm
20. The diameter of a solid shaft made of mild steel, rotating at 250 r.p.m, is 45 mm. The shaft is designed to transmit 50 kW. What will be the factor of safety if the ultimate shear stress at yield is 427 N/mm2?
(a) 6
(b) 5
(c) 4
(d) 3
21. Consider that a wire rope is subjected to the following stresses :
1. Direct stress on account of axial force
2. Bending stress
3. Stress due to acceleration of the moving mass
Which of the above are correct?
(a) 1 and 2 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3
22. When a shaft rotates in anti-clockwise direction at high speed in a bearing, it will
(a) move towards right of the bearing making metal to metal contact
(b) have contact at the lowest point of the bearing
(c) move towards left of the bearing making metal to metal contact
(d) move towards left of the bearing making no metal to metal contact
23. The load on a gear tooth is 50 kN. If the gear is transmitting a torque of 6000 N m, the diameter of the gear is approximately (consider pressure angle as 20° and cos 20° = 0-94)
(a) 0.5 m
(b) 0.75 m
(c) 1 m
(d) 0.25 m
24. In a particular application, the shaft is subjected to bending loads and also large axial loads. The bearing suitable for supporting such a shaft is
(a) thrust bearing
(b) tapered roller bearing
(c) ball bearing
(d) spherical roller bearing
25. A hole of diameter 35 mm is to be punched in a sheet metal of thickness t and ultimate shear strength 400 MPa, using punching force of 44 kN. The maximum value of t is
(a) 0.5 mm
(b) 10 mm
(c) 1 mm
(d) 2 mm
26. Two principal tensile stresses of magnitudes 40 MPa and 20 MPa are acting at a point across two perpendicular planes. An oblique plane makes an angle of 30° with the major principal plane. The normal stress on the oblique plane is
(a) 8.66 MPa
(b) 17.32 MPa
(c) 35.0 MPa
(d) 60.0 MPa
27. If Mohr's circle is drawn for the shear stress developed because of torque applied over a shaft, then the maximum shear stress developed will be equal to
(a) diameter of the Mohr's circle
(b) radius of the Mohr's circle
(c) half of the radius of the Mohr's circle
(d) 1.414 times radius of the Mohr's circle
28. The modulus of rigidity and the bulk modulus of a material are found as 70 GPa and 150 GPa respectively.Then
1. elasticity modulus is 200 GPa
2. Poisson's ratio is 0.22
3. elasticity modulus is 182 GPa
4. Poisson's ratio is 0.3
Which of the above statements are correct?
(a) 1 and 2
(b) 1 and4
(c) 2 and 3
(d) 3 and 4
29. Consider the following statements
1. Cross-section of a member of truss experiences uniform stress.
2. Cross-section of a beam experiences minimum stress.
3. Cross-sectionof a beam experiences linearly varying stress.
4. Cross-sections of truss members experience only compressive stress.
Which of the above statements are correct?
(a) 1 and 2
(b) 1 and 3
(c) 1 and 4
(d) 3 and 4
30. A steel rod, 2 m long, is held between two walls and heated from 20 °C to 60 °C. Young's modulus and coefficient of linear expansion of the rod material are 200 x 103 MPa and 10 x 10`6 /° C respectively. The stress induced in the rod, if walls yield by 0.2 mm, is
(a) 60 MPa tensile
(b) 80 MPa tensile
(c) 80 MPa compressive
(d) 60 MPa compressive
31. A tension member of square cross- section of side 10 mm and Young's modulus E is to be replaced by another member of square cross- section of same length but Young's modulus E/2. The side of the new square cross-section, required to maintain the same elongation under the same load, is nearly
(a) 14 mm
(b) 17 mm
(c) 8 mm
(d) 5 mm
32. An aluminium bar of 8 m length and a steel bar of 5 mm longer in length are kept at 30 °C. If the ambient temperature is raised gradually, at what temperature the aluminium bar will elongate 5 mm longer than the steel bar (the linear expansion coefficients for steel and aluminium are 12x 10-6/°C and 23x 10-6/°C respectively)?
(a) 50.7 °C
(b) 69.0 °C
(c) 143.7 °C
(d) 33.7 °C
33. A close-coiled helical spring of 10 active turns is made of 8 mm diameter steel wire. The mean coil diameter is 10 cm. If G = 80 GPa for the material of spring, the extensionof spring under a tensile load of 200 N will be nearly
(a) 40 mm
(b) 45 mm
(c) 49 mm
(d) 53 mm
34. If a thin-walled cylinder with closed hemispherical ends with thickness 12 mm and inside diameter of 1250 mm is to withstand a pressure of 1.5 MPa, then the maximum shear stress induced is
(a) 19.5 MPa
(b) 39.05 MPa
(c) 78.12 MPa
(d) 90.5 MPa
35. A 4 m long solid round bar is used as a column having one end fixed and the other end free. If Euler's critical load on this column is found as 10 kN and E = 210 GPa for the material of the bar, the diameter of the bar is
(a) 50 mm
(b) 40 mm
(c) 60 mm
(d) 45 mm
