Top Mechanical Engineering Interview Objective Questions
1. A hollow shaft of same cross-section area as solid shaft transmits
A. Same torque
B. Less torque
C. More torque
D. Unpredictable
Answer:
B. Less torque
2. In a cantilever beam, maximum deflection occurs at where
A. Bending moment is zero
B. Bending moment is maximum
C. Shear force is zero
D. Slope is zero
Answer:
A. Bending moment is zero
3. In a rectangular beam, when width, depth and length are doubled, the bending stress will be
A. Shall remain unchanged
B. Shall be doubled
C. Shall become ¼ th
D. Shall be halved
Answer:
C. Shall become ¼ th
4. In an I –section beam, the bending moment is resisted mainly by
A. Flanges only
B. Web only
C. Both by flanges and web
D. None of the above
Answer:
B. Web only
5. In internal combustion (I.C.) engines, combustion of fuel takes place in
A. Outside the cylinder
B. Inside the cylinder
C. Not in the cylinder
D. None of the above
Answer:
B. Inside the cylinder
6. Power available at the shaft of an I.C engine is known is
A. Brake horse power
B. Indicated horse power
C. Net indicated horse power
D. Pumping power
Answer:
A. Brake horse power
7. In internal combustion engine piston the maximum temperature occurs at
A. Ring section
B. Gungeon pin
C. Bottom centre
D. Top centre
Answer:
A. Ring section
8. A two-stroke engine is generally preferred to a four-stroke engine because
A. It offers low fuel consumption
B. It gives lesser shocks and vibrations
C. It can be easily started
D. It has smaller size for the same output.
Answer:
D. It has smaller size for the same output.
9. During idling process, a petrol engine requires
A. Lean mixture
B. Rich mixture
C. Variable mixture
D. None of above
Answer:
A. Lean mixture
10. Cavitation in a pipe will begin when
A. Pressure at any location reaches pressure equal to the saturated vapour pressure of liquid
B. Pressure becomes more than critical pressure
C. Flow is increased
D. Pressure is increased
Answer:
A. Pressure at any location reaches pressure equal to the saturated vapour pressure of liquid
11. Capillary action of liquid is due to the
A. Viscosity of liquid
B. Cohesion of liquid particles
C. Surface tension
D. Adhesion of liquid particles on the surface
Answer:
B. Cohesion of liquid particles
12. In one ton refrigeration machine, the term “one ton” implies
A. One ton refrigerant is used
B. One ton water can be converted into ice
C. One ton ice when melts from and at 0oC in 24 hours, the refrigerating effects is equivalent to 3000 kcal/hour
D. None of the above
Answer:
C. One ton ice when melts from and at 0oC in 24 hours, the refrigerating effects is equivalent to 3000 kcal/hour
13. In a refrigeration cycle, the moisture content is to be removed before it enters into which system
A. Cold side of system
B. Evaporator
C. compressor
D. condenser
Answer:
B. Evaporator
14. What is the difference between Pipe and Tube?
Ex.
Iron Pipe, Carbon Tube, Steel Tube etc.
· Tube is defined by Outer diameter and Wall thickness (OD and WT). While Pipe is defined by Inner diameter (ID).
Example:
2 inch pipe have 2.375 inch outer diameter, where 2 inch tube have same 2 inch outer diameter.
· Tube is easily shaped by bending, where Pipe needs some mechanical work to shape it.
· Tube is tight then Pipe.
· Tube is applicable to non cylindrical sections like Square and Rectangular.
15. Is gate valve used for Throttling?
Gate valves are not suitable for throttling because the control of flow is difficult for the valve’s design, and the flow of fluid slapping against a partially open gate can cause extensive damage to the valve.
16. Why is the Suction pipe of Vapour Compression Refrigeration system insulated?
1. It prevents the suction line from sweating and dripping water inside the house.
2. The insulation also prevents the suction line attracting heat from the outdoors on its way to the condenser coil.
17. How does Welding damage Eye sight?
An Electric welding arc produces Ultraviolet light and the UV light (Sun burn) will damage the retina. Welding shields or Goggles with the proper shade (Automatic shading) of lens is the best protection for welders.
Light filtering curtains and reduced reflective surfaces help protect both welders and observers in the area.
18. Explain why BCC, FCC and CPH lattice packing and features of grain structure affect the Ductility and Brittleness of parent metallic materials?
Ductility is the mechanical property of a material. (It is the material’s ability to deform under the tensile stress without fracture). So it is depends on the atoms how they arranged in a lattice and its grain size. The ability to absorb the energy of the impact and fracture resistance depends on the arrangement of the atoms in a lattice and features of grain structure.
19. Why do you have Truss Bridges?
Truss bridges carry load in tension and compression rather than bending (Self weight + The weight of vehicles crossing it + Wind loads). A truss has the ability to dissipate a load through the truss work. The beams are usually arranged in a repeated triangular pattern, since a triangle cannot be distorted by stress.
20. Why I-section beam is preferred for heavy loading?
Cross sectional shape I, giving many benefits. It is very good for giving stiffness (less deformation on loading) and to withstand higher bending moments (as a result of heavy loading) on comparison with other cross-sectional shapes of same area. Also, it is very easy to manufacture. It will have more moment of inertia.
21. What is difference between Center of Mass and Center of Gravity?
Both terms are same when gravity is uniform. When gravity is non-uniform following are the terms:
The center of mass is a point that acts as if all the mass was centered there (the mass on one side of the point is equal to the mass on the opposite side). If supported at the center of mass, an object will be balanced under the influence of gravity.
The center of gravity is the point at which where the sum (vector) of the gravitational forces act on an object which will be balanced on that point.
22. What is the difference between Center of Mass and Centroid?
If the material composing a body is uniform or homogeneous, the density or specific weight will be constant throughout the body, and then the centroid is the same as the center of gravity or center of mass.
Centroid:
Centroid is the point, where the whole area of plane is going to be act. It is valid only for 2D problems like plane figures, square plate etc.
The center of mass is a point that acts as if all the mass was centered there (the mass on one side of the point is equal to the mass on the OPPOSITE side). If supported at the center of mass, an object will be balanced under the influence of gravity.
23. What are the differences between Weight and Mass?
Mass is a measure of how much matter an object has. Mass is specified in Gram or Kilograms.
Weight is a measure of how strongly gravity pulls on that matter. Force is measured in Newton’s.
F=m.g
Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.
24. What is the difference between Projectile motion and a Rocket motion?
A projectile has no motor/rocket on it, so all of its momentum is given to it as it is launched. An example of a projectile would be pen that you throw across a room.
A rocket or missile does have a motor/rocket on it so it can accelerate itself while moving and so resist other forces such as gravity.
In mechanics point of view projectile don’t have any particular shape it is a point mass. Whereas rocket has a particular shape and hence it has center of gravity situated at particular point on its body. Therefore rocket motion comes under kinetics and projectile comes under kinematics.
25. What type of cooling used in High Voltage Transformer?
The big transformers you find on power poles usually use oil as a dielectric insulator, in smaller HV transformers, like the ones in TV’s are usually filled with resin.
26. What is honing of Cylinder Liners?
The honing equipment used has been manufactured by “Chris Marine”. The head of the honing device consists of four synchronized stones. For the initial honing diamond stones are used to break up the hardened surface in the scuffed areas. For the main honing very coarse and hard stones are used to produce a very desirable rough surface all over the liner.
The advantage, especially for the 2-stroke engines, is possibility to save the liner after a seizure, scuffing or blow-by or even to eliminate the ovality of the liner. Another advantage is that it is possible to machine a rough liner wall to obtain a well oiled surface.
27. What is the difference between Speed and Velocity?
Speed is scalar quantity and Velocity is a vector – velocity has both speed and direction.
Speed is expressed as distance moved (d) per unit of time(t). Speed is measured in the same physical units of measurement as velocity, but does not contain an element of direction. Speed is thus the magnitude component of velocity.
28. Difference between Yield Stress and Yield Strength?
Stress is a measure of the load applied to a sample relative to a cross sectional area of the sample. Strength is a quantification of the samples ability to carry a load. The terms “yield strength” and “yield stress” of a material are usually used interchangeably (correct or not).
It is the stress which will just cause the material to plastically deform. If a material yields at 30,000 psi, the yield stress is 30,000 psi. If the part in question has a cross sectional area of 2 square inches, the strength at yield would be 60,000 pounds, but usually we just say the yield strength is 30,000 psi.
29. What is the difference between Yield and Ultimate tensile strength?
The yield strength is reached when the material becomes Non – linear (that is non elastic) and takes a permanent set when load is released. Material stretches but does not break. Ultimate strength is when it breaks and is higher than yield strength.
30. What is the difference between Flexural strength and Tensile strength?
Flexural strength is resistance offered against bending. Tensile strength is resistance offered against tensile force.
31. What is the difference between Shear and Tensile strength?
Tensile Strength for a Bolt is determined by applying a Force along it long axis. Shear Strength for a Bolt is determined by applying a Force across its diameter, as it would be loaded in a lug joint. Tensile strength is strength in tension when pulling force is applied. And shear strength is strength against cutting force which is known as shear force.
32. What is the difference between Tensile strength and Tensile modulus?
Tensile strength is the ultimate capacity of the material to resist a tensile load regardless of deflection.
Tensile modulus also known as Young’s modulus is a measure of the stiffness of an isotropic elastic material. It is defined as the ratio of the uni-axial stress over the uni-axial strain. It is determined from the slope of a stress-strain curve traced during tensile tests conducted on a sample of the material.
34. Normalizing operation is carried out in
a) Water
b) Oil
c) Air
d) Furnace
Ans.: c) Air
35. The main purpose of heat treatment of steels is to change the
a) Chemical composition
b) Mechanical properties
c) Surface finish
d) Physical properties
Ans.: b) Mechanical properties
36. Which of the following is a non-destructive test
a) Impact test
b) Charpy test
c) Cupping test
d) Radiography test
Ans.: d) Radiography test
37. Polymerization is associated with
a) Stainless steel
b) Cast iron
c) Thermoplastic
d) Duralumin
Ans.: c) Thermoplastic
38. The material of pattern in the investment casting is
a) Resin
b) Sand
c) Wax
d) Wood
Ans.: c) Wax
39. Shell moulding process requires
a) Wooden pattern
b) Plastic pattern
c) Sand pattern
d) Metal pattern
Ans.: d) Metal pattern
40. Liquid nitrogen containers can be made from
a) Ferritic stainless steel
b) HSLA steel
c) Titanium
d) Austenitic stainless steel
Ans.: d) Austenitic stainless steel
41. Stretching of rolled rings is done to
a) To meet dimensional requirement
b) To relieve stresses
c) To introduce stresses
d) To improve finish
Ans.: b) To relieve stresses
42. During manufacturing of spring, the coiling pitch is assumed to be larger than specified pitch by
a) 5-8%
b) 10-12%
c) 2-5%
d) none
Ans.: a) 5-8%
43. Metric thread have included angle:
a) 60°
b) 55°
c) 30°
d) None
Ans.: a) 60°
44. The crater wear of a cutting tool is due to
a) Chemical action of the coolant
b) Excessive heat generated during cutting operation
c) Rubbing of tool against the work piece
d) Abrasive action of the chip
Ans.: d) Abrasive action of the chip
45. Crater wear is predominant in
a) Carbon tool steels
b) Tungsten carbide tools
c) High speed steel tools
d) Ceramic tools
Ans.: b) Tungsten carbide tools
46. Identify the single point cutting tool
a) Milling cutter
b) Hacksaw blade
c) Grinding wheel
d) Cutting tool used in a slotting machine
Ans.: d) Cutting tool used in a slotting machine
47. The angle between the tool face and the plane parallel to the base of the cutting tool is called
a) Lip angle
b) Cutting angle
c) Rack angle
d) Shear angle
Ans.: c) Rack angle
48. In metal cutting operation, the cutting angle is defined as the angle
a) between the flank and the horizontal machined surface
b) between the shear plane and the direction of tool travel
c) between the face of tool and the line tangent to the machined surface at the cutting point
d) between the tool face and the ground end surface of flank
Ans.: c) between the face of tool and the line tangent to the machined surface at the cutting point
49. The angle between the face and the flank of the single point cutting tool is known as
a) Rack angle
b) Clearance angle
c) Lip angle
d) Point angle
Ans.: b) Clearance angle
50. Cutting tool may be provided with large positive rack angle to
a) Have a better heat dissipation
b) Avoid rubbing with the finished surface
c) Increase the strength of cutting edge
d) Reduce the magnitude of cutting forces
Ans.: d) Reduce the magnitude of cutting forces
51. Single point thread cutting tool should ideally have
a) Zero rack angle
b) Positive rack
c) Negative rack
d) Normal rack
Ans.: a) Zero rack angle
52. With an increase in nose radius of single point cutting tools
a) Tool life increases
b) Excessive heat is generated
c) Surface finish deteriorates
d) Cutting speeds have to be kept small
Ans.: a) Tool life increases
53. Tool signature
a) Is a pictorial view of the tool
b) Outlines the orthographic projection of the tool
c) Represents complete specification of the tool
d) Is a numerical method of tool identification
e) Indicate life of tool
Ans.: d) Is a numerical method of tool identification