Torque, : The turning effort applied to the shaft, as that of steam engine by the various cranks, .The term originated in electrical engineering. ,Torque efficiency,: The ratio of the actual torque of a motor the torque which it would exert if free from frictional forces,. Torsion,: In mechanics, that force with which a thread wire or rod of any material depends to return to state of rest after being twisted. (2) The act of turning or twisting or the state of being twisted. Tensional stiffness,: In mechanics that the amount of rigidity of a shaft by which it is enabled to resist ,not simply such strains would produce actual twisting off but also such excessive vibrations as would prevent it from doing it work with due steadness. ,Torsional strain, : The effect setup in the body by the torsional stress which tends to rupture it by twisting one fiber around an other. Torsional strength: Resistance to being twisted or wrenched off in direction about its axis as in case of shafting. Engine: Compound machine. ,Diesel engine ,: A diesel engine is an oil engine which uses low grade oil and iginates this fuel by the heat of air compression. ,Petrol engine, : It is an engine that require high grade oil, gasoline and ignites it by an electric spark after the gasoline has been mixed with air in carburetor and compressed. ,Weir ,: it is defined as it the full of the vessels or tank the water flows over the wall is called weir. Pascal law: it states that intensity of pressure at any point in a fluid (liquid +gas) at rest ,is the same in all direction. ,Piezo meter, : it is simple from manometer it is used to measure the moderate pressure. ,Vaccum,: Any pressure which is less than atmospheric pressure is known as vaccum . ,Simple manometer ,: simple manometer is an instrument or improved from piezo meter it is like U shape .It has two limbs this instrument measures the medium neither very small nor very large + ve and negative pressure., Hydrostatic,: The term of hydrostatic meaning the study of pressure exerted by liquid. ,Total pressure,: F/A=W/A ,Bernoullis equation:,For parallel in compressed liquid flowing in continuous stream .,The total energy ,of the particle remains the same while the particle moves from one point to an other provided no friction., Notch,: An opening is one side of the tanks like large orifice with the up stream liquid level below the top edge of the opening.