However a temperature difference exists within a system or when two systems at different temperatures
are brought into contact, energy is transferred. The process by which the energy transport takes place is
known as heat transfer. Heat cannot be measured or observed directly, but the effect it produces is
amenable to observation and measurement.
The study of forces and flow within fluids.
Theory of Machines deal with the study of relative motion between various elements of a machine and the forces which act on them.