# Pressure Problem

1. Nov 14, 2007

### jamesyboy1990

1. The problem statement, all variables and given/known data

$$\frac{r^{4}p(pi)}{8cl}$$

where:
l = the length of the tube in cm
r = the radius of the tube in cm
p = the difference in pressure of the two ends of the tube in dynes per cm2
c = the coefficient of Viscosity in poises (dyne-seconds per cm2)
v = volume in cm3 per second
pi = 3.14159..... (i couldn't get the symbol to appear)

I am doing an experiment in which i measure viscosity for different liquids. However, i'm having problems in obtaining value "p". I know that pressure is force times area. In this case, area should be the cross sectional area for the tube at one end, and the cross sectional area of the valve opening at the other end (if i'm not mistaken). However, what will be the force?

2. Relevant equations

$$\frac{r^{4}p(pi)}{8cl}$$

where:
l = the length of the tube in cm
r = the radius of the tube in cm
p = the difference in pressure of the two ends of the tube in dynes per cm2
c = the coefficient of Viscosity in poises (dyne-seconds per cm2)
v = volume in cm3 per second
pi = 3.14159..... (i couldn't get the symbol to appear)

3. The attempt at a solution

I know that pressure is force times area. In this case, area should be the cross sectional area for the tube at one end, and the cross sectional area of the valve opening at the other end (if i'm not mistaken). However, what will be the force?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 16, 2007

### rl.bhat

Take a bottle of about 20 cm height with one opening at the bottom.Put tube of diameter 1mm in a cork which fits the opening at the bottom. Now fill the liquid in the bottle, and note down the height of the liquid surface from the center of the horizontal tube. Nosw the pressure will be rho*g*h.