mass and energy analysis of control volumes
The product is the energy transported into control volume by mass per unit time. Many engineering systems such as power plants operate under steady conditions. Under steady-flow conditions, the volume, the mass and energy contents of a control volume remain constant.
Devashish Kottana
introduction to basic concept of thermodynamics
In classical thermodynamics, the second law is a basic postulate applicable to any system involving heat energy transfer; in statistical thermodynamics, the second law is a consequence of the assumed randomness of molecular chaos.
Stress and strain
When a stretching force (tensile force) is applied to an object, it will extend. We can draw its force - extension graph to show how it will extend. Note: that this graph is true only for the object for which it was experimentally obtained. We cannot use it to deduce the behaviour of another object even if it is made of the same material. This is because extension of an object is not only dependent on the material but also on other factors like dimensions of the object (e.g. length, thickness etc.) It is therefore more useful to find out about the characteristic extension property of the material itself. This can be done if we draw a graph in which deformation is independent of dimensions of the object under test. This kind of graph is called stress- strain curve.