Mechanical Properties Of Fluids Flashcards
1 ATM =
1.013 × 10⁵ Pa
Pascal’s law
Pressure in a fluid at rest is the same at all points if they are all at the same height
F(a)/P(a) = F(b)/P(b)
P(a) = P(b)
Whenever ext pressure is applied at any part of a fluid, it is transmitted equally to all directions.
mg =
(P2-P1)A, A is area if base of container
P2 - P1 =
Rho g h
Pressure diff depends on
Vertical dist h
Mass density
Acceleration due to g
P=
Pa + rho gh
Gauge pressure
Excess of pressure(P - Pa) at depth h
Pressure of atmosphere at any point
Weight of Column of air of unit cross sectional area extending from that point to top of atmosphere
Open manometer
Measure pressure diff
Consists of a suitable liquid I.e a low density liquid(for oil) for measuring small pressure diff & high density liquid(mercury) for large pressure diff
What is incompressible?Why?
Liquids;
Due to less intermolecular force of attraction, they acquire the shape of the container. Its volume doesn’t change with pressure
Streamline flow
Path taken by fluid under steady flow.
It is a curve whose tan at any point is in direction of fluid velocity at that point.
Equation of continuity
A(p)V(p) = A(r)V(r) = A(q)V(q) at points P,Q,R
Bernoulle’s principle
As we move along a streamline, sum of pressure(P), K.E/unit volume & U.E(potential)/unit volume(rho gh) remains a constant
Limitations of Bernoulli’s theorem
- Ideally applies to fluids with 0 viscosity & non viscous fluids
- Doesn’t hold for non steady or turbulent flows
- Fluids must be incompressible as elastic energy of fluid is not taken
Bernoulli’s equation
P1 + ½rho V1² + rho gh1 = const
Torricelli’s Law formula
V1 = (2gh)½
Viscosity
Resistance to fluid motion when solid moves on a surface
Coefficient of viscosity + formula
Shear stress to strain rate
η=Fr/Av = Fl/vA
If Temp increases viscosity of fluids
Decreases
But increases for gases
Stoke’s law
F = 6pi eta aV, a is radius of sphere
Terminal velocity + formula
Highest velocity attained by an object falling through a fluid
vT = √(2gh)
Terminal vel depends on:
Square of radius a of sphere & viscosity of medium
Surface tension
Phenomenon: as liquids don’t have shape but volume, they acquire a free surface when poured, the surface has some additional energy
Surface tension
Tension of surface of a liquid caused by attraction of the particles in the surface by the bulk of the liquid, which tends to minimise surface area
