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# 30+ Common Mechanical Interview Questions & Answers

Worrying about a Mechanical Interview and many things to cover your mind for preparation? Here are 30+ Frequently asked common questions and answers to boost your confidence level.

Many questions depend upon the type of industry you are preparing an interview for, In this blog, we are covering the most common questions in each industry.

If you have any questions in mind or like to share your interview experience, please comment below!

## 1. What Is The Law Of Thermodynamics?

1st Law of Thermodynamics – Energy cannot be created or destroyed.

2nd Law of Thermodynamics – For a spontaneous process, the entropy of the universe increases.

3rd Law of Thermodynamics – A perfect crystal at zero Kelvin has zero entropy.

## 2. What are stress and strain?

Stress is the force acting on the unit area of a material. The effect of stress on a body is called strain.

Stress can result in the deformation of the body. Strain is the measurement of how much an object is stretched or deformed due to the stress developed in the object.

## 3. What is the young modulus?

Young’s Modulus of a material is a fundamental property of every material that cannot be changed.

It is dependent upon temperature and pressure, however.

The Young’s Modulus (or Elastic Modulus) is in essence the stiffness of a material. In other words, it is how easy it is bent or stretched.

## 4. What is a mechanism example?

A mechanism is usually a piece of a larger process, known as a mechanical system or machine.

Sometimes an entire machine may be referred to as a mechanism; examples are the steering mechanism in a car or the winding mechanism of a wristwatch.

## 5. What is 2s and 4S engine?

In a 2-stroke engine, all five functions of the cycle are completed in only two strokes of the piston (or one revolution of the crankshaft).

In a 4-stroke engine, the five functions require four strokes of the piston (or two revolutions of the crankshaft).

## 6. What is the purpose of a spark plug?

A spark plug is used as a source of ignition, as the “spark” in its name implies.

It is a key component of internal combustion engines and its primary function is to ignite a fuel/air mixture within the combustion chamber of a car or other system.

## 7. What is  Angular Momentum?

Angular momentum is defined as The property of any rotating object given by moment of inertia times angular velocity.

It is the property of a rotating body given by the product of the moment of inertia and the angular velocity of the rotating object.

## 8. What is the role of nitrogen in welding?

A nitrogen hot air welder uses compressed nitrogen gas to eliminate oxygen from the weld area.

The nitrogen acts as a shielding gas and allows for a contaminant-free weld with less smoke, which creates a stronger weld.

## 9. What is the difference between a turbine and a centrifugal pump?

The main difference between a turbine pump and a typical centrifugal pump is its impeller design.

Compared to most centrifugal pumps, turbine pumps have smaller diameter impellers with rows of numerous small vanes.

These vanes recirculate the fluid as it travels from the suction end to the outlet.

## 10. What does the turbocharger do?

It is the job of the turbocharger to compress more air flowing into the engine’s cylinder

When air is compressed the oxygen molecules are packed closer together.

This increase in the air means that more fuel can be added for the same size naturally aspirated engine.

## 11. How does the refrigerator works?

Refrigerators work by causing the refrigerant circulating inside them to change from a liquid into a gas.

This process, called evaporation, cools the surrounding area and produces the desired effect.

You can test this process for yourself by taking some alcohol and putting a drop or two on your skin.

## 12. What is the thermostat in a refrigerator

The thermostat is designed to regulate temperature to chill food and beverages.

If items don’t seem as cool as they should be, reset the refrigerator thermostat by raising it a degree.

It should then turn on or restart. But if it does not, there may be a technical malfunction.

## 13. Where is shaft coupling used?

The shaft coupling is a mechanical component that connects two rotating shafts, such as the driving shaft and the driven shaft, to transmit power.

It is used in motors, pumps, generators, and compressors.

## 14. What is the Otto cycle?

The Otto cycle is a cycle of engine operation which requires four strokes of the piston: induction, compression, ignition, and exhaust.

The fuel and air mixture is compressed before combustion is started by an electrical spark or other means.

Named after German engineer Nikolaus Otto.

## 15. What is a cooling tower used for?

Cooling towers are primarily used for heating, ventilation, air conditioning (HVAC) and industrial purposes.

Cooling towers provide a cost-effective and energy-efficient operation of systems in need of cooling.

## 16. What do Gd and t mean?

GD&T is an acronym that stands for Geometric Dimensioning and Tolerancing

It is a symbolic language used by designers to communicate manufacturing constraints and tolerances.

This information is conveyed in the form of annotations included in the design of the part.

## 17. What is the meaning of P and ID?

A piping and instrumentation diagram, or P&ID, shows the piping and related components of a physical process flow.

It’s most commonly used in the engineering field.

## 18. What is an alloy with examples?

Alloy is a metal made by combining two or more metallic elements, especially to give greater strength or resistance to corrosion.

They are homogeneous mixtures of two or more substances.

An example of an alloy is the tin in the mixture of copper and tin that makes bronze.

## 19. What do you mean by knurling?

Knurling is the metal modification process of creating small ridges along a metal object’s surface to improve the ease with which such an object can be physically handled, lifted or gripped.

## 20. What is engineering drawing?

An engineering drawing is a type of technical drawing that is used to convey information about an object.

A common use is to specify the geometry necessary for the construction of a component which is called a detailed drawing.

Usually, many drawings are necessary to completely specify even a simple component.

## 21. What is Orthographic Drawing?

An orthographic projection is a way of representing a 3D object by using several 2D views of the object.

Orthographic drawings are also known as multi-views. The most commonly used views are the top, front, and right side.

## 22. What is pitting in material?

Pitting corrosion is a localized form of corrosion by which cavities or “holes” are produced in the material.

Pitting is considered to be more dangerous than uniform corrosion damage because it is more difficult to detect, predict and design against.

## 23. What is a double pulley called?

A block and tackle or only tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads.

## 24. What are the Newtonian and non-Newtonian fluids?

Newtonian fluids obey Newton’s law of viscosity. The viscosity is independent of the shear rate.

Non-Newtonian fluids do not follow Newton’s law and, thus, their viscosity (ratio of shear stress to shear rate) is not constant and is dependent on the shear rate.

## 25. What is enthalpy & entropy?

Enthalpy is the measure of total heat present in the thermodynamic system where the pressure is constant.

Entropy is the measure of disorder in a thermodynamic system.

## 26. What are the basic shaft and basic hole?

Basic hole means the whose lower limit is basic size. and basic shaft means whose upper deviation is zero.

## 27. How do you calculate the least count?

The smallest value that can be measured by the measuring instrument is called its least count.

## 28. What is torque and its unit?

Torque is the expression of a rotational or twisting force.

The unit newton metre is properly denoted N⋅m.

## 29. What is the difference between pipe size and tube size?

The tube is measured by outside diameter, the pipe is measured by inside diameter.

## 30. What is the latent heat value?

It is the amount of heat needed for a unit mass of a given body to change its temperature by one degree.

## 31. What is calorific value?

Calorific value is defined as the number of calories generated when a unit amount of substance is completely oxidized and is determined using the bomb calorimeter.

## 32. What are the main types of steel?

The four main types are:

• Carbon steel.
• Stainless steel.
• Alloy steel.
• Tool steel.

## 33. What metal is stainless steel?

Stainless steel is an iron and chromium alloy.

While stainless must contain at least 10.5% chromium, the exact components and ratios will vary based on the grade requested and the intended use of the steel.

## 34. What is cavitation in pumps?

Cavitation is the formation of bubbles, or cavities, in a liquid, developed in areas of relatively low pressure around an impeller.

## 35. Define the buckling factor?

The buckling Factor is defined as the ratio of the equivalent length of the column to the minimum radius of gyration.

## 36. What is the process of heat treatment?

Heat treatment is the process of heating metal without letting it reach its molten, or melting, stage, and then cooling the metal in a controlled way to select desired mechanical properties.

Heat treatment is used to either make the metal stronger or more malleable, more resistant to abrasion or more ductile.

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