phy53 lecture  		dr. brown		11 november 2010

review -- flow [laminar,uniform] ... venturi effect ... develop bernoulli equation

flow:  
I_v = A v = "volume" current   ;  multiply by density to get "mass" current

conservation of mass and incompressible fluid gives A_1 v_2 = A_2 v_2


venturi effect: 
the pressure decreases where fluid velocity increases

explains airplane upward thrust on wing [airfoil], etc.
paper rises as air blown across top of dangling piece of paper


bernoulli:
P + \rho g h + \frac{1}{2} \rho v^2 = constant

comes from work = \Delta K  or work by fluid = \Delta E_{mechanical}

energy per unit volume = units of pressure

[to get more precise - handling more complex fluid flow would need Navier-Stokes thm]

problem examples:
pressurized tank with spout above tank

Torricelli's Law...coming

open tank with small hole [facuet] near bottom -- velocity of fluid coming out is \sqrt{2gh}

Drag forces at inside surface of pipe...velocity gradient from outside to; requires work to keep fluid moving..so

(P_1 - P_2) = I_v R    where R is the "resistance" of the pipe

"Ohm's Law" for fluid in pipe
 
what if large diameter?
what if pipe longer?

viscocity ... reynold's number  ... laminar vs turbulent flow ... you can hear turbulent flow in blood vessels via stethescope [sp]...
blood thinners reduces viscocity 
  

introduce...new topic,,,picture of solid...atoms connected via springs;  apply force to each end look at amount it stretchs...