Which type of shaft is preferred for power transmission,solid or hollow one?Hollow shaft utilize material strength more efficiently, so hollow shaft used if you concerned about

weight. 

But, when weight is not a concern, solid shaft is better (stronger, of course), easy to fabricate.

What is structurally stronger, solid steel or hollow steel?If a solid and hollow shape have the same outside dimensions, the solid one is clearly stronger. 

The reason you see so many hollow sections is that they have an incredibly higher strength/weight

ratio and can resist the same load with much less material used.

What will be the difference in torsional strength of hollow shaft & solid shaft of same outer diameter at equal load.Compare the polar moment of inertia of the solid cross section to the hollow cross section. You’ll find

that the difference between the two is equal to the polar moment of inertia of the portion removed

from the hollow section.

The deflection of the shaft under a torsional load would be the product of the torsional load and the

length of the shaft divided by the product of Polar Moment of inertia and modulus of rigidity of the

shaft: theta=TL/JG.

What are the units for Poisson’s ratio?It is a unit less quantity. Because it is one quantity divided by another quantity of the same units. 

In fact, even the parent quantities that define Poisson’s ratio are unit less. Strain has no units.

What is the difference between Stress and Pressure?Stress=Resistive force/Area.

Pressure=Force/Area.

Stress is pull force and Pressure is push force.

1.Heat Treatment Process HRC Stands for 2.Material OHNS Stands for

HRC Stands for –Rockwell Hardness C scale

OHNS Stands for — Oil Hardenable Non Shrinkage steel

Function of Fly wheelFlywheel stores the Kinetic Energy during the idle portion of the work cycle,and delivers this Kinetic

Energy during peak-load.

Bullet Proof Glass is made up of which material?Bulletproof glass is usually constructed using a strong but transparent material such as polycarbonate

thermoplastic or by using layers of laminated glass. The desired result is a material with an

appearance and light-transmitting behavior of standard glass but offers varying degrees of protection

from small arms fire. The polycarbonate layer, usually consisting of products  such as Cyrolon, Lexan

and Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate

provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides

little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet

and thereby prevents penetration. This type of bullet-resistant glass is usually 70-75 mm thick.

Difference between Performance and Efficiency?Performance is the measure of quality of the work done by any machine. better  the quality better will

be the performance of that machine. while efficiency is the ratio of desired output to the required

input for any machine.

Performance is about the quality that a machine or plant is producing suppose there are two

machines, first produces the job of accuracy .002mm and the second one produce product of the

accuracy .001mm. then the second one will have higher performance.  while efficiency is the ratio of

the o/p to the i/p. if same machines are producing 200 and 100 product per day respectively for the

same i/p,then the eff. of the first machine will be high.

What are the causes of main engine black smoke?There is many cause of black smoke.

1. It’s improper mixture of fuel supply by carburetor like very rich mixture so the fuel improper burn.

2. It’s when piston or piston ring is fail so back side cooling oil release in combustion chamber it

cause black smoke.

3. Improper ignition system like not sufficient time of pressure rise delay period .

Poisons ratio is higher in (rubber/steel/wood)When a material is compressed in one direction, it usuallytends to expand in the other two directions

perpendicular tothe direction of compression. This phenomenon is called thePoisson effect. Poisson’s

ratio is a measure of the Poisson effect.

For rubber = 0.5

For steel = 0.288

For wood < 0.2

Thus Poisson’s ratio is higher in RUBBER.

1. What is the importance of the Thermodynamics in the field of Mechanical Engineering? 

All the mechanical engineering systems are studied with the help of thermodynamics. Hence it is very

important for the mechanical engineers.

2. How many Laws of Thermodynamics are there? 

There are three laws of the 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.

Second Law: When two isolated systems in separate but nearby regions of space, each in

thermodynamic equilibrium in itself, but not in equilibrium with each other at first, are at some time

allowed to interact, breaking the isolation that separates the two systems, and they exchange matter

or energy, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies

of the initial, isolated systems is less than or equal to the entropy of the final exchanging systems. In

the process of reaching a new thermodynamic equilibrium, entropy has increased, or at least has not

decreased.

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

minimum.

3. State Laws of conservation of energy? 

According to the laws of conservation of energy, “energy can neither be created nor be destroyed. It

can only be transformed from one form to another.”

4. Is the boiler a closed system? 

Yes definitely the boiler is a closed system.

5. What is Carnot engine? 

It was being designed by Carnot and let me tell you that Carnot engine is an imaginary engine which

follows the Carnot cycle and provides 100% efficiency.

6. Which formula forms a link between the Thermodynamics and Electro chemistry? 

Gibbs Helmholtz formula is the formula which forms the link between the thermodynamics and

electromagnetism.

∆Hs/R = [∂ lnp /∂ (1/T)]x

where: x – mole fraction of CO2 in the liquid phase 

p – CO2 partial pressure (kPa) 

T – temperature (K) 

R – universal gas constant 

α – mole ratio in the liquid phase (mole CO2 per mole of amine)

7. Which is the hardest compound known? 

Diamond.

8. What is Hess Law? 

According to the Hess law the energy transfer is simply independent of the path 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.

9. Which has more efficiency: Diesel engine or Petrol engines? 

Off course Diesel engine has the better efficiency out of two.