# Mechanical Engineering Interview Questions

1) Explain the second law of thermodynamics.
Answer- The second law of thermodynamics says that the entropy of the universe increases over time and moves towards a maximum value.

2) What kinds of pipes are used for steam lines?
Answer- Normally galvanized pipes are not used for steam. Mild steel with screwed or welded fittings is the norm. The pressure and temperature are very important factors to be considered in deciding what type of materials to be used. Steam even at low pressures can be extremely dangerous.

3) Write the difference between the shear center flexural center of twist and elastic center.
Answer- The shear center is the centroid of a cross-section. So the flexural center is the center of twist, which is the point on a beam that you can add a load without torsion. The elastic center is located at the center of gravity. If the object is homogeneous and symmetrical in both directions of the cross-section, then they are all said equivalent.

4) What is ferrite?
Answer- Magnetic iron rock

5) Differentiate between projectile motion and rocket motion.
Answer- A projectile has no motor or rocket on it, so all of its momenta is given to it when it is launched. An example of a projectile can be a 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 it resist other forces such as gravity.

6) What is the alloy of tin and lead?
Answer- A tin and lead alloy are commonly known as solder. Usually, solder is a wire with a rosin core used for soldering and the rosin core acts as a flux.

7) What does F.O.F. stand for in the piping design?
Answer- FOF stands for Face of Flange. A flange has either of the two types of faces:
• Raised face
• Flat face
The F.O.F is used to know about the accurate dimension of the flange to avoid minute errors in the measurement in case of vertical or horizontal pipelines.

8) Explain the Otto cycle.
Answer- It was designed by Nicolas Otto, a German engineer. It can be explained by a pressure-volume relationship diagram. It shows the functioning cycle of a four stroke engine. The cycle starts with an intake stroke, closing the intake and moving to the compression stroke, starting of combustion, power stroke, heat exchange stroke where heat is rejected and the exhaust stroke.

09) What is the gear ratio?
Answer- Gear ratio is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

10) What is annealing?
Answer- It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. It increases the hardness and strength if the material.

11) What is the ductile-brittle transition temperature?
Answer- It is defined as the temperature below which the tendency of a material to fracture increases rather than forming. If the temperature is less than this, the material loses its ductility. It is also called Nil Ductility Temperature.

12) What is a uniformly distributed load?
Answer- A UDL or uniformly distributed load is a load, which is spread over a beam in such a way that each unit length is loaded to the same extent.

13) What is enthalpy?
Answer- Enthalpy is the heat content of a chemical system.

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