Fundamental Concepts of Fluid Mechanics

·         Mechanics : Deals with action of forces on bodies at rest or in motion.

·         State of rest and Motion: They are relative and depend on the frame of reference.  If the position with reference to frame of reference is fixed with time, then the body is said to be in a state of rest.  Otherwise, it is said to be in a state of motion.

·         Scalar and heater quantities: Quantities which require only magnitude to represent them are called scalar quantities.  Quantities which acquire magnitudes and direction to represent them are called vector quantities.

Eg: Mass, time internal, Distance traveled à Scalars

            Weight, Displacement, Velocity à Vectors

·         Velocity and Speed: Rate of displacement is called velocity and Rate and distance traveled is called Speed.

Unit: m/s

·         Acceleration: Rate of change of velocity is called acceleration. Negative acceleration is called retardation.

·         Momentum: The capacity of a body to impart motion to other bodies is called momentum.

The momentum of a moving body is measured by the product of mass and velocity the moving body

Momentum = Mass x Velocity

Unit: Kg m/s

·       Newton’s first law of motion: Every body continues to be in its state of rest or uniform motion unless compelled by an external agency.

·       Inertia: It is the inherent property the body to retain its state of rest or uniform motion.

·       Force: It is an external agency which overcomes or tends to overcome the inertia of a body.

·       Newton’s second law of motion: The rate of change of momentum of a body is directly proportional to the magnitudes of the applied force and takes place in the direction of the applied force.

·       Mass:   Measure of amount of matter contained by the body it is a scale of quantity.

                        Unit: Kg.   

                                                                   

·       Weight:  Gravitational force on the body. It is a vector quantity.

                        F = ma

                        W = mg

                        Unit: newton (N)                    g = 9.81 m/s²

·       Volume:  Measure of space occupied by the body.

                        Unit: m³

                                1 m³ = 1000 litres

·       Work:  Work done = Force x Displacement  à Linear motion.

                  Work done = Torques x Angular displacement  à Rotatory motion.

Unit: Nm or J

·       Energy:  Capacity of doing work is called energy.

Unit: Nm or J