Properties of metals

 

Properties of metals : 

1 . Elasticity : It is the property of material to regain in original shape after deformation  when the      external forces are removed.

2. Plasticity : It is the property of material which retain the deformation produce under load permanently.

3. Ductility : It is the property of the material enabling it to be drawn into a wire with the application of a tensile force.

4. Brittleness : It is the property of breaking of a material with little permanent distortion .

5. Malleability : It is a special case ductility which permit materials to be rolled or hammered into thin sheets.

6. Toughness : It is the property of a material to resist fracture due to high impact loads like hammer blows .

Laws of Thermodynamics

 Three laws of thermodynamics :

   1. Zeroth law of thermodynamics :This law states that when two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other.  

   2. First law of thermodynamics :This law states that the heat and mechanical work are mutually          convertible. According to this law, a definite amount of mechanical work is needed to produce a definite amount of heat and vice versa.                                                                                                                            This law is also states that the energy can neither be created nor destroyed , through it can be transformed from one form another. According to this law, the energy to the heat supplied(Q) must be balanced by the external workdone(W) plus the gain in internal energy(E) due to rise in temperature.                                          Q = W + E  

  3. Second law of thermodynamics : This law states that there is definite limit to the amount of mechanical energy, which can be obtained from a given quantity of heat energy.                                                 The second law of thermodynamics has also been stated by Kelvin-Planck as "It is impossible construct an engine working on a cyclic process, whose sole purpose is to convert heat energy in to work." According to this statement, the second law of thermodynamics is sometimes called as law of degradation of energy.                                                                                                       

                                                  

Newton's law of motion

 Newton's three laws of motion: 

  1. Newton's first law of motion . It states that everybody continues in the state of rest or of uniform      motion, in a straight line, unless it is acted upon by same external force.

  2. Newton's second law of motion . It states that the rate of change of momentum directly               propotional to the impressed force, and takes place in the same direction, in which the force acts.  

  3. Newton's third law of motion . It states that  to every action, there is always an equal and opposite reaction.                                

Stress & strain

Stress : When some external system of forces or loads act on a body ,the internal forces( equal & opposite) are setup various sections of the body, which resist the external forces .This internal forces per unit area at any section of the body is known as unit stress or simply stress.

             Stress,  σ = P/A   (where,  P = Force or load acting on the body , A= Cross-section  area of the body )

         S.I. unit of stress is expressed in Pascal (Pa). 

Strain : When a system force act on a body, it undergoes some deformation .This deformation per  unit length is known as unit strain or simply strain .

                 Strain,  ε =  δl/l (where, δl = change in length of the body , and  l = original length of body.)