Mechanical Engineering interview questions and answers - part 6


Mechanical Engineering interview questions and answers - part 6

Part 1   Part 2   Part 3   Part 4   Part 5   Part 6

What is mechanism?

A mechanism is an assembly of different parts which perform a complete motion and is often part of a machine.

State Newton's three laws of Motion.

- The law of inertia: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
- Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Force=Mass times acceleration.
- For every action there is an equal and opposite reaction.

State the laws of thermodynamics and its importance of in Mechanical Engineering.

Thermodynamics is a physical science which studies the interrelation between heat, work and the internal energy of any system. Thermodynamics helps study all the systems of mechanical engineering. There are three laws of thermodynamics.

First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same.

Eg: turning on a light would seem to produce energy; however, it is electrical energy that is converted.

Second Law: The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases.

Eg: A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car.

Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.

Eg: Water in gas form has molecules that can move around very freely. Water vapor has very high entropy (randomness). As the gas cools, it becomes liquid which can still move around but not as freely. At this point they have lost some entropy. On cooling further it becomes solid ice where molecules can no longer move freely but can only vibrate within the ice crystals. The entropy is now very low. As the water nears absolute zero, the vibration of the molecules diminishes. If the solid water reaches absolute zero, all molecular motion would stop completely. And at this point the water would have no entropy at all.

What is Hess law?

According to the Hess law the energy transfer is simply independent of the way being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

What is PS?

Personal Statement. It is something that gives an informative background about an individual.

What is a bearing? What are the different types of bearings?

Bearing is a device that helps smoother movement with minimal friction which in turn helps enhances efficiency and speed. Considering two types of loading, radial and thrust, there are different types of bearings which help handle these loads. The basic difference in the types of loads is essentially due to their ability to handle weight and different kinds of loads for various applications. Different types of bearings are:

-Ball bearing
-Roller bearing
-Ball Thrust bearing
-Roller thrust bearing
-Tapered roller bearing
-Magnetic bearings
-Giant Roller Bearing

What is a process flow diagram?

A Process Flow Diagram is a user friendly, simplified sketch which illustrates general plant streams, major equipments and key central loops and shows the relationship between major components in the system. By using symbols to identify instruments and vessels it describes the primary flow course. They also provide e detail of mass/energy balance data along with stream composition and physical properties, however do not show minor components.

What is a time and motion theory?

Frederick Taylor was pioneer of the time and motion theory. This technique monitors the amount of time required to complete a task along with observing the steps taken by a worker to complete the given task.

Which is the hardest material on earth?

Diamond is currently the hardest material, made up of carbon atoms which cannot move. Carbon is the only atom that can have four electrons in the second shell surrounding the carbon nucleus, precisely why making a diamond the hardest material. However, there also are claims by a few to a new rare material called Wurtzite Boron Nitride which has a structure similar to a diamond but has some other atoms in place of carbon.

One unit of BTU is how many Joules?

1 BTU=1055.06 Joules

What does a pump develop? Give reason to support your answer.

Pump is a device that is used to transfer fluid from one place to another place which means it develops flow not pressure.

Explain the difference between pipe and a tube.

A pipe is measured based on its inner diameter (ID) whereas a tube is measured based on the outer diameter (OD). Other than the dimensions there is no major difference between the two.

Explain the formula of heat loss in a pipe.

In order to find total heat loss through the pipes it is imperative to know the thermal conductivity and the differing thicknesses of each layer. The ground that surrounds the pipe also acts as a layer of insulation. Considering this, the thermal properties of the stoneless sand is included in the heat loss calculation.

What kind of pipes are used for steam lines?

Pressure and temperature are two of the most important factors to be considered before selecting the type of material to be used. Steam is a compressible gas due to which the capacity of the pipe line depends on the size of the pipes and pressure of the steam. Since steam at even low pressure can be dangerous, extra care is to be taken. Galvanized pipes are usually not used for steam. Pipes made of mild steel with welded fittings are instead largely used.

Who invented the four stroke engine? According to you which one is more efficient, four stroke engine or a two stroke engine and why?

Nikolaus Otto invented the four stroke engine. Both, two stroke and four stroke have their own advantages and disadvantages. 4 stroke is more fuel efficient. However, 2 stroke produces more power.

What do you understand by the concept of a 6 stroke engine? Explain how it works.

The six stroke engine is based on the concept of four stroke engine but built with an intention of improvising the efficiency in reducing emission. Every cycle of a four stroke engine involves the upward and downward movement of the piston which happens twice in the chamber, resulting in four total strokes and one of which is the power stroke which provides the torque to move the vehicle. A six stroke engine works similarly except that there are two power strokes.

Explain what is torque

Torque is the force that causes rotation. It is a measure of how much force is acting on an object making it rotate.

What is the difference between torque and power?

While power determines the speed of a vehicle, torque determines the time in which that speed can be reached. The greater the torque figure, the faster the acceleration. The more torque in the engine, the faster you accelerate. Power is the rate at which work is done, so it is basically the potential of the engine.

Explain why diesel engine is known as high torque and petrol engine as high speed engine?

Each power stroke in a petrol engine releases more heat and is converted into mechanical energy due to a higher rate of burning. This is the reason petrol engine has higher power and acceleration.

Diesel engine is a compression ignition engine with higher compression ratio, therefore extreme pressure is high. Since the piston of a diesel engine is larger, more torque is delivered in produced.

Why do heavy vehicles use diesel engine?

The compression ratio of diesel engine is higher than the petrol engine, the reason for producing higher torque. The efficiency of diesel engine increases with load. Diesel produces slow energy on burning of fuel and the efficiency of the engine increases with load which is why diesel engine is suitable and largely used for heavy vehicles.

Explain the difference between projectile motion and rocket motion.

The major difference is that a projectile has no motor or a rocket on it, due to which the momentum is given to it as it is launched. A pen thrown across a room is a classic example of a projectile motion. On the other hand, a rocket or missile has a motor on it which helps in accelerating while moving. This helps in resisting other forces such as gravity. A projectile does not have any specific shape, it is a point mass, whereas rocket has a particular shape having its center of gravity situated at a particular point on its body. Thus rocket motion comes under kinetics and projectile comes under kinematics.

Between steel, copper and brass, which conduct faster heat.

Copper conducts heat faster than steel or brass. In most cases, material that is good for conducting heat is also good for electricity.

Explain the types of sensors.

(i) Temperature Sensor- This device collects information about the temperature from a source and converts it to a form which is understandable by another device or person. Glass thermometer is the best example where mercury acts as the temperature sensor.

(ii) IR Sensors- This device detects and/or emits infrared radiation to sense a particular phase in the environment. Mostly thermal radiation is emitted by all the objects in the infrared spectrum. This type of radiation is not visible to the human eye but the infrared sensor detects it.

(iii) UV Sensors- These sensors measure the intensity of the ultraviolet radiation. This form of electromagnetic radiation has wavelengths which are longer than x-rays yet shorter than visible radiation. UV sensors can discover the exposure of environment to ultraviolet radiation.

(iV) Touch Sensor- A touch sensor acts as a variable resistor based on the location where it is sensed. Proximity Sensor- A proximity sensor detects the presence of objects that are placed in close proximity without any point of contact.

What minerals are used in the manufacture of cars?

Cars are made from many various minerals. The steel body is made from the iron-rich minerals like magnetite and hematite. Door handles and badges are often coated in chromium which comes from chromite. Some of the other minerals used are aluminum, quartz, copper, magnesium, zinc, tin etc.

Which instrument measures speed in a car?

A speedometer helps measure the speed in the car.

What are the advantage and disadvantage of using LPG in a car?


The high octane rate enables it to blend better with air and to burn completely, generating less carbon. With less carbon buildup, spark plugs often last longer and oil changes are needed less frequently.

Since it burns in the gaseous phase, it results in less corrosion and engine wear.

In case of a spill, LPG evaporates quickly.


The LPG requires servicing at approximately once a year.

Since complete combustion occurs, more heat is liberated which is not advised for a long journey as the engine will get over heated.

Installation of LPG is rather difficult.

Why gas containers are mostly in a cylindrical shape?

The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.

Explain why re-heater is used in gas turbine

The advantage of reheater is that it significantly increases the thrust; which is a prime reason for its use in gas turbines.

How many types of suspensions are used in automobiles?

McPherson struts
Leaf spring
Coil spring
Torsion beam
Air Suspension

What is DTSI? Why it is used in motor bikes?

Digital Twin Spark Ignition. This is used for a better fuel combustion in the cylinder head which helps provide better efficiency and optimum use of fuel.

What are the advantages of DTSI over normal engines?

The cylinder head has two spark plugs, instead of the usual one. When two sparks are generated at either ends of the combustion chamber, the air-fuel mixture is ignited in a way that creates two flame fronts. A higher rate of combustion is achieved leading to higher rise in pressure. The outcome of this is more torque, better fuel efficiency and lower emissions.

What is meant by gear ratio?

A gear ratio is a direct measure of ratio of the rotational speeds of two or more interlocking gears.

What is the ratio of specific heat of air?

The ratio of specific heat γ=CP/CV is a factor in adiabatic engine processes and in determining the speed of sound in gas. This ratio γ=1.66 for an ideal monoatomic gas and γ=1.4 for air, which is predominantly a diatomic gas.

What is the percentage of carbon present in pig iron?

Carbon content is generally 3.5-4.5%.

Part 1   Part 2   Part 3   Part 4   Part 5   Part 6

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santosh modekar 08-2-2015 07:20 AM


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what about Pferdestarke?huh? brake horse power stuff??

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stephin 03-5-2015 07:04 AM

Part6 Answers

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Lucy 03-3-2015 04:58 AM

question answers

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Trenton 02-27-2015 01:08 AM

25 Interview Questions

Part 6 indicated that there were questions and answers. The answers for part 6 do not appear to be part of the information. Please send ASAP, Thank you

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part 6 answers

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Answers to part 6

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Request to send part 6 questions Answers.

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Md. Nur Alam 12-2-2014 11:29 AM


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PART 6 Answers

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sidhu 02-14-2014 03:18 AM

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more questions and answers

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oliver 12-30-2013 09:21 AM


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ramana 10-9-2013 10:43 AM

mechanical interview Questions

Very very thanx for sharing this usefull interview question.... Its my humble request.....plz ...plzz... Provide us the answers for Part-6.
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Ashif Sekh 09-9-2013 05:25 AM

Regarding Part 6

Please send me the answers for Mechanical Engineering interview questions and answers - part 6

Avinash 08-23-2013 08:22 AM

plese send answer of part 6 page que

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md.hakim 07-22-2013 02:09 AM

Kind request to upload the answer...

Can you please upload the answers for those questions which shown above...?

harish 07-18-2013 06:57 AM


thanks please tell me the answers of all the questions

shammi choudhary 07-13-2013 09:50 AM

requesting answers for above 40 questions

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ARUN REDDY 06-21-2013 10:31 AM


Plz put up more commipitive questions took.
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Vikram.R 05-31-2013 09:06 AM

Request to send answers for 40 questions...

Hi... Good work... can u give me some more basic questions in mechanical engineering with answer.ans also send the answers for the 40 questions.

suresh 05-28-2013 04:51 AM



praveen 05-2-2013 01:02 AM

can u tell me where is the answers for 40 questions?

please post some more questions with answers

anitha 02-28-2013 08:41 AM


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