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### Most Commonly Asking Mechanical Engineering Interview Question...

1. What is the difference between projectile motion and a rocket motion?

Ans :- 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.

2. What is gear ratio?

Ans :-
It is the ratio of the number of revolutions of the pinion gear to one revolution of the idler gear.

3.What is annealing?

Ans :- It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

4. What is representative elementary volume?

Ans :- Smallest volume over which measurements can be made that will yield a representative of the whole.

5. What is the percentage U238 in nature?

Ans :- 99.2745%

6. Difference between 'Thermodynamics and Heat Transfer' ?

Ans :-
Thermodynamics mainly deals with the transfer of energy in form of heat or work between systems and surroundings with other systems in form of either heat or work in equilibrium conditions. When there is change in one state, which was in equilibrium state and starting to change in other equilibrium state, this information helps to determine heat or work interactions due to this process. While

Heat transfer deals with non equilibrium heat exchange or transfer due to temperature gradient while in thermodynamics, during thermal equilibrium (No temperature gradient) no heat exchange is possible. [Read more interview questions on Thermodynamics]. Heat never transfer when there is no temperature gradient.

7. Why are LNG pipes curved?

Ans :- LNG pipes are curved because LNG is condensed gas (-164 deg cel) so it can expand the pipes that is what engineers designed the LNG pipes are curve type.

8. How does iron ore turn into steel?

Ans :- To make Steel, Iron Ore is refined into iron and all the carbon is burned away using very high heat (Bessemer). A percentage of Carbon (and other trace elements) are added back to make steel.

9. What is knurling?

Ans :- Knurling is a machining process normally carried our on a centre lathe. The act of Knurling creates a raised criss-cross pattern on a smooth round bar that could be used as a handle or something that requires extra grip.

10.What are the points in the stress strain curve for steel?

Ans :- Proportional limit, elastic limit or yield point, ultimate stress and stress at failure.

11. What is isometric drawing?

Ans :- It is a 3-D drawing used by draftsmen, architects etc

12. What is Hess Law?

Ans :- 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.

13.Which is the hardest compound known?

Ans :- Diamond.

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

Ans :-  Diesel engine has the better efficiency out of two.

15. State Laws of conservation of energy?

Ans :- 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.”

16. Why entropy change for a reversible adiabatic process is zero ?

Ans:- Because there is no heat transfer in this process.

17. What are two essential conditions of perfect gas ?

Ans:-  It satisfies equation of state and its specific heats are constant.

18. What is the difference between scavenging and supercharging ?

Ans:-  Scavenging is process of flushing out burnt gases from engine cylinder by introducing fresh air in the cylinder before exhaust stroke ends. Supercharging is the process of supplying higher mass of air by compressing the atmospheric air.

19. What are the standard sizes of drawing board as per Indian Standards?Ans :-

As per Indian Standards : 1250×900,900×650,650×500,500×350,350×250 sizes are available.

20. What are the methods of extinguishing fire ?

Ans :-  1) Starvation. Separating or removing the burning material from the neighbour hood of the fire.

2) Blanketing. Preventing the air flow to the fire.
3) Cooling. Lowering the heat created by burning materials.