 # Basic Laws of Fluid Mechanics (Basic Concept of Fluid Mechanics Part-1)

### Their intermolecular forces are low and fluid continuously undergoes deformation.

#### Density or mass density (ρ): It is defined as the ratio of mass of the fluid to its volume.It’s unit is kg/m³.

##### Note: Density of water 1000kg/m³ ### Density variation with temperature and pressure.

#### Specific weight or weight density (γ): It is defined as the ratio of weight of the fluid to its volume.It’s unit is N/m³. #### It’s is dimensionless. #### Specific volume : It is defined as the ratio of volume per unit mass.It’s unit is m³/kg. ## Pascal’s Law:

#### According to this law pressure at a point in static fluid( fluid at rest) is equal in all directions. ## Hydrostatic’s Law

##### According to this law, the rate of increase in pressure in a vertical direction is equal to the weight density of the fluid at that point.  Now integrating the above expression from z = 0 to z = h  then pressure at depth h is given by

### Now let’s discuss few cases to measure the gauge pressure.

#### 1. We want to find the pressure at point B in the following figure:

As we have discussed above that pressure at C will be given by Hydrostatic law

Pc = ρgh

and by pascal’s law Pressure at any point in same level will be same i.e.

Pb = Pc = ρgh #### 2. We want to find the pressure at point B in the following figure:

By pascals law pressure will be same along A-A’  line.

Now applying hydrostatic law we can write  #### 3. We want to find the pressure between points A& B in the following figure:

By pascals law pressure will be same along C-C’  line.

Now applying hydrostatic law we can write  #### 4. We want to find the pressure at point B in the following figure:

By pascals law pressure will be same along C-C’  line.

Now applying hydrostatic law we can write  ### I hope you like this section. Please share with friends and like my Facebook page and never miss an update.

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