CBSE Class 11-science Physics Mechanical Properties of Fluids
Pressure in FluidsPressure in fluids
Equation of ContinuityIf the fluid velocity < critical velocity, the flow is steady or streamlined.
If the fluid velocity > critical velocity, the flow becomes turbulent.
Equation of continuity : Area of cross section times velocity = Constant.
Fluid speed is greater in narrow regions as compared to wider regions.
Bernoulli's PrincipleBernoulli's principle holds true in case of ideal fluid flow which is incompressible, irrotational and streamlined.
Bernoulli's Principle: the sum of the pressure, the kinetic energy per unit volume and the potential energy per unit volume remains constant.
Bernoulli's Principle: Applications1. The speed of efflux from a hole in an open tank is given by andradic;2gh
2. Venturimeter: Device used to measure the flow speed of an incompressible liquid. Based on Bernoulliandrsquo;s principle.
3. Magnus effect: Curving in the path of the ball introduced due to the difference in pressure above and below the ball.
Non-Ideal Fluids1. Viscosity is internal friction in a fluid. In laminar flow the flow is steady, and in turbulent flow there is no steady state pattern.
2. Stokeandrsquo;s law states that the frictional force on a particle is Fd = 6hp Rv
3. Terminal velocity is given by Vs = 2/9[( rp andndash; rf)/h]gR2
Surface TensionSurface tension : Energy required per unit increase in surface area of the surface film.
Angle of contact : Angle formed between the solid/liquid interface with the liquid/vapour interface.
Surface Tension and Capillarity1. Excess pressure inside the drop and a gas bubble: Pi - Po = 2S/r
2. Excess pressure inside the soap bubble Pi - Po = 4S/r andnbsp;andnbsp;andnbsp;andnbsp;
3. Height of liquid column rising in a capillary tube h = 2Scosandtheta;/andrho;gr
where andrho; is the density of liquid (mass/volume), g is acceleration due to gravity (length/time2) and r is radius of tube (length).