MECHANICAL ENGINEERING QUESTIONNAIRE
Q1. Give reasoning for decrease in temperature as we move higher.
Ans. The earth can be considered as isochoric system that is volume of air is constant around our globe. As at constant volume the pressure is directly proportional to temp. as a result temp will also decrease as pressure decreases as we move higher and higher.
Q2. Explain heat exchanger and its usage.
Ans. A heat exchanger (HX) is used for exchanging heat between two mediums i.e fluids.
Its consists of following two groups;
1. Inirect Contact HX
2. Direct Contact HX
In other words, heat exchanger is a device used for heat dissipation from a certain part where excess heat may can prove to be harmful to the system.
It increases the heat dissipation by simply exposing more area to the atmosphere as the heat transfer directly depends on the availability of area for heat transfer. For instance, fins on the engine cylinder
Q3. Differentiate between stress and pressure?
Ans. Pressure is exerted only in case of fluid or liquid or gases whereas stress is applied only on solid.
Q4.Expain how can we find bearing number or bearing size?
Ans. We can find bearing number or bearing size through a commercial catalog for some companies like SKF or by reading the size on the cylinder block
Q5. What “psi” represent?
Ans. psi is an abbreviation for pounds force per square inch and can be commonly seen on pressure gauges as unit.
Q6. Define four stroke engine?
Ans. In four stroke engine there are two valves i.e. one is inlet and another is exhaust. The stroke is done one by one in sequence as suction, compression, power and exhaust and for every four stroke there is one power.
Q7. Differentiate between a pipe and tube?
Ans. Pipe is usually denoted by OD x gauge. Pipe is used to transfer liquid or gas. Pipe is flexible. Pipe is disignated with its Inner dia.
Tube is denoted by ID which is NB x sch.Tube is used to transfer Heat. Tube is Rigid and is disignated with Outer Diameter.
Q8. What will be the consequence when water flowing through pipe is suddenly cut?
Ans. When water flowing through a pipe is suddenly stopped, a pressure wave eqiuvalent to sound will get created and will move to and fro. It causes damage to pipe by suddenly hitting the pipe wall which is known as water hammering
Q9. Amongst four stroke engine or a two stroke which one is more efficient? Why?
Ans. Since there is one power stroke for every 2 strokes in 2-Stroke engine, it is more efficient and compact for same power generation although four stroke engine is more frequently used.
Q10. If I have a thermal flask in which i have to fill the boiled water. Along with I also have thermocol, saw dust and silver paper. Arrange these materials to attain minimum heat loss.
Ans. The arrangement can be thermal flask outside silver paper outside saw dust and finally thermocol because thermal condutivity of silver is more than sawdust and thermal conductivity of saw dust is more than thermocol arrangement is like this.
Q11. Explain the four basic quantities in engineering mechanics?
Ans. Length, time, mass and force are the four basic quantities in engineering mechanics.
Length is required to locate the position of a point in space and hence describe the size of a physical system .
Time is taken as a sucession of events. The principles of statics are time dependent and play an important role in the study of dynamics.
Mass is property of matter and using it we can compare the action of one body with that of another.
Force is considered as a push or pull which is exerted by one body on another body.
Q12. Explain viscosity ?
Ans. Viscosity is the measure of the resistance of a fluid which is being deformed by either shear stress or tensile stress. It is “internal friction”. Water and petrol are “thin” because they have lower viscosity, whereas honey is “thick” because it has higher viscosity
Q13. Define Mechanical Engineer?
Ans. Mechanical Engineer is a discipline of engineering which applies the principles of physics and materials science for manufacturing, design, analysis, and maintenance of mechanical systems. It is the branch of engineering that encompasses the generation and application of heat and mechanical power and also in the design, production, and use of machines and tools.
Q14. Why you chose mechanical branch?
Ans. It is the Power Centre of Technical field and is very dynamic in nature. It started with to do something afresh. So mechanical engineering is just different from all other branch with its merits on other.
Q15. Define autocad?
Ans. It is very important for engineers and uses 3d drawings, solids modeling, wire frame modeling, fast working, 2D drawings etc
Q16.Define Electrical motor maximum speed?
Ans. RPM (ROTATION PER MINUTE) determines it.
Q17. Explain the method to find the amount of natural gas required to generate 1 kwhr of energy?
Ans. It can be found by heat rate of power plant run by natural gas divided gross calorific value of the natural gas.
Q18. Explain the procedure to check wheather a gear and pinion are properly aligned or not for both running and static condition?
Ans. It can be checked by the shaft(axis) of the pinion and gear must in 90 degree.
Q19. What do you think is boiler a closed system?
Q20. Explain Hess Law?
Ans. According to this, the energy transfer is simply independent of the path followed. The same amount of energy will be dissipated or absorbed if the reactant and the product of the whole process are the same.