Mechanical study point

 Fourier's Law of heat conduction: A iron plate which have area is A and thickness of plate x , temperature of plate is T1 and atmosphere temperature is T2 ,Q heat is transfer to plate from atmosphere temperature   within time t so  According to this law : . Heat (Q) is directly proportional to area of of plate and temperature difference  of plate and atmosphere , and inversely   proportional to plate thickness (x). Q ~ A(T1-T2) /x so,              Q is heat and  A is area,  T1 is temperature of plate and  T2 is Temperature of  atmosphere  &  x is the plate thickness 

Poisson ratio : It is ratio of  lateral strain to the longitudinal strain   is is represented by miu u . u = dL/lD   Relation between their constants Relation Between E & nita (n) : E = 2n (1+1-2u) Relation between E & K : E = 3K(1-2u) poisson ratio for  steel  0.33, rubber =0.5 Cork =0 metal =0.32~0.35

 Hook's law :   According to the hook's law statement is stress is directly proportional to the   strain within the elastic limit is called hook's law . Stress ~ strain  Stress = E strain E is hook's constant its means elastic constant  so  stress  = F/A , Strain =  l/L where l is changing length and L is original length E =Stress /Strain E = Fl/AL

  Stress :   Stress is the physical quantity its results on  material which is resist the internal molecule deforming force  per unit area .that is called stress .it is measure in Newton per unit area. it is represented by o- (Sigma) . Let the the force F act on the body per unit area so stress will,  Stress = F/A Stress =  Deforming force /unit area  There are types of stress 1. Longitudinal stress : it is results of tension force  per unit area.  o- = Ft /Area  2. Compressive stress : it is results of compressive force per unit area. o- = Fc /Area    

  Enthalpy :   Enthalpy is the property of system which represent  the total energy of system. In total energy of system  is internal energy , potential energy, kinetic energy, heat energy, etc  Or  the summation of all energy of system is called enthalpy of system.                  H  = U + W  Where   H  = enthalpy  , U internal energy, W =          work done  . 

  Second law of thermodynamics:  Clausius statement : It state that, it is impossible to construction of system, heat can never transfer to coller body to warmer body without any external device.  Kelvin planks statement :  It is impossible to construction a machine which total heat  energy is convert into mechanical energy or useful  Rejection heat should zero  Heat energy is equal to mechanical energy  Efficiency = 100% 

  Thermodynamics first law :  According to first law of thermodynamics, its state that the heat energy givenor taken to the system is equal to sum of internal energy and work done on system or by the system.  It is based on conservation of energy.             Q   =   U + W  Where Q  heat of system             U internal energy of system           W  work done by the system or on system            Q   =  U + P ∆V         W =  P∆V       P  : pressure,  ∆V  : changing volume   Case 1.  If in cyclic process   :  Internal energy of cyclic process is zero   So        Q   = W    

 Galusek law :  According to this law the volume Of gase is directly proportional to temperature of gase at constant pressure.    Let volume Of gase  V anda temperature T so                            P    €     T  For two gase    P1, T1 and P2 , T2                             P1 V1 /T1   = P2 V2 /T2                          P1  = P2                     V1 / T1  =   V2 /T2  

  Boyles law :  According to Boyle's law the absolute pressure of gase is inversely proportional to volume Of gas at absolute temperature.                P €  1/  V As shown in figure  Graph between pressure and volume  Hyperbolic graph Conditions For two gase  Let pressure P1 and temperature V1 for first gase and second gase have pressure P2 and volume V2  .  So    P1V1 / T1  = P2V2/T2       So     T1=  T2   Results     P1V1 = P2V2  Charles law :  According to Charles law the pressure of gase is directly proportional to absolute temperature at constant volume  As               P  €   T   Conditions for two  gases P1, T1 and second gase P2, T2               So            ...

  Thermodynamics property :  In thermodynamics system which have mass and energy pressure, temperature, volume.  There are two thermodynamics property  1. Extensive property :  It is the property of system which is only depends on mass of system.  Example : volume, energy, work, enthalpy entropy etc  2. Intensive property :  It is the property of system which is not only depends on mass of system  Example: specific volume, specific energy, pressure, Temperature etc 

  Thermodynamics system :   In this system has some pressure , temperature and volume where thermodynamics activity are performed  Example : pistons cylinder arrangement, boiling of water, etc  There are three systems  1. Close system  In this mass is not a transfer but energy is transfer to other systems.  Example: Cooking of food in pressure cooker 2. Open system:  In this system, mass and energy both are transfer to other system.  Example: boiling of water in open pan  3. Isolated system :  In this system, energy and mass both are not transfer to the system.  Example : universal system is isolated system