The term fluid refers to a substance that can flow and does not have a
shape of its own. For example liquid and gases
The pressure p is defined as the magnitude of the normal force acting on a unit surface
Railway tracks are laid on large sized wooden or iron sleepers. This is
because the weight (force) of the train is spread over a large area of the
sleeper. This reduces the pressure acting on the ground and hence prevents
the yielding of ground under the weight of the train.
Weight of the small element dh is balanced by the excess pressure. It means
if the pressure in a liquid is changed at a particular, point the change is transmitted
to the entire liquid without being diminished in magnitude.
Hydraulic brake system is used in auto-mobiles to retard the motion
To measure the atmospheric pressure experimentally, torricelli invented a mercury barometer
Let us suppose water is used in the barometer instead of
Liquid Placed in elevator :
When elevator accelerates upward with acceleration a0 then pressure in
the fluid, at depth ‘h’ may be given by
The path taken by a particle in flowing fluid is called its line of flow. In the case of
steady flow all the particles passing through a given point follow the same path
and hence we have a unique line of flow passing through a given point which is
also called streamline
The equation of continuity expresses the law of conservation of mass in fluid
ENERGY OF A LIQUID
A liquid can posses three types of energies
It states that the sum of pressure energy, kinetic energy and potential
energy per unit mass or per unit volume or per unit weight
(i) Bunsen burner
(ii) Lift of an airfoil.
It is a gauge put on a flow pipe to measure the flow of speed of a liquid (Fig). Let the liquid of density
? be flowing through a pipe of area of cross section A1. Let A2 be the area of cross section at the
throat and a manometer is attached as shown in the figure. Let v 1 and P1 be the velocity of the flow
and pressure at point A, v2 and P2 be the corresponding quantities at point B.