Que: What happens if gasoline
is used in a Diesel engine?
Diesel engine will work ?

Ans: No, It will not work,as the Compression ratio of Petrol engine is 6 to 10 & that of Diesel engine is 15 to 22. Thus on such high compression, gasoline gets highly compressed & it may blast.

Que: What is the function of chill in casting?

Ans: Chill are used in casting for direction solidification, in some casting cooling rate are uneven so some part cool higher than other at this situation some metal partical are put at low cooling place so cooling rate are increased.

જવાબ  : કાસ્ટિંગમાં ચીલનું કાર્ય સુ છે? 
ચિલનો  દિશા ઘનીકરણ માટે નિર્ણાયક ઉપયોગ કરવામાં આવે છે,  કેટલીક કાસ્ટિંગમાં  ઠંડક દર અસમાન હોય છે, જેથી કેટલોક  ભાગ બીજા ભાગ કરતા વધુ ઠંડો થાય છે, આ પરિસ્થિતિમાં અમુક મેટલ પાર્ટિકલ ઠંડક દર અસમાન હોય ત્યાં મુકવામાં આવે છે જેથી ઠંડક દર સમાન થાય જાય છે, જેથી ઠંડક દર સમાન કરવા મુકવામાં આવતા મેટલ પાર્ટિકલને ચિલ કહે છે,

Que: What happen if DIESEL used in PETROL engine?

Ans: This is not true. Diesel is much harder to ignite than petrol and relies on very high compression (5-10 times greater than a petrol engine) to superheat air in the cylinders and thus trigger ignition. Consequently the fuel is injected just prior to TDC (top dead center). Petrol is injected on the down stroke  compressed on the upstroke and burns when ignited by the spark plug.
Diesel contains much longer chain hydrocarbons and is much "heavier" and less volatile. It doesn't burn completely in the petrol engine resulting in smoking (when part of a fuel mixture) to complete non-running as the mixture is enriched.
Petrol introduced into a diesel engine burns immediately it is blown in and with the wrong dynamics, making the engine run badly and unevenly, potentially causing damage.

Que: What is the 1st class, 2nd class & 3rd class lever?

It uses a fulcrum in between, and the applied force and load are at opposite ends.
________________________________________________________________

The second class lever is one where the fulcrum is at one end, and the applied force at the other. The load that is to be moved is between them.
________________________________________________________________

The fulcrum is once again at one end of the lever, but this time the load is at the other end, and you apply a force in between.

________________________________________________________________

Que: What is TDC and BDC in internal combustion (IC) engine?

Ans:  TDC (top dead center) means the upper most position of piston in cylinder & BDC (bottom dead center) means maximum lower position of piston in IC engine.

Que: In mountain it isn't easily possible burning of fuel (wood, coal.,etc) than in land, Why?

Ans:  Because of at top of the mountain pressure of air are lower than earth as this reason air density also lower so less oxygen there than land level and burning of fuel required oxygen so easily burning are not possible. 

Que: What do you mean by VISCOSITY?

Ans: Viscosity is the measure of the internal friction of a fluid. This friction becomes apparetn when a layer of fluid is made to move relatively to another layer. The greater the friction the greater the amount of force required to cause this movement which is called shear. Shearing occurs whenever the fluid is physically moved by pouring, spreading, spraying, mixing, etc. High viscous liquids require more force to move than less viscous liquids.

Que: How fuel are burnt in major diesel engine and why not used spark plug?

Ans: Mostly Diesel are burnt in diesel engine by compression and so it is broadly known "CI-COMPRESSION IGNITION" engine. Burning of fuel are happen because of when piston moves up in close cylinder chamber it is compressed so as per law of boyle and charles temperature of air also increased at last when fuel are injected due to internal temperature of air it is burning.

પોલીથેન ની કોથળી માં પાણી ભરી આગ પર રાખવાથી પણ બળતી નથી કેમ? 

કેમ કે પાણી તું ઉત્કલનબિંદુ ૧૦૦ અંશ છે અને કોથળી નું તેના થી વધારે છે માટે આગ ની ગરમી જે પોલેથીન ને મળે છે તે પાણી ને transfer થાય છે અને પાણી ૧૦૦ અંશ કરતા વધુ ગરમ થઇ શકાતું નથી જેથી પોલીથીન પણ ૧૦૦ અંશ કરતા વધારે ગરમ થતું નથી.