# Chapter 4 : Measures Of Pressure¶

## Example 4.1 Page No : 85¶

In [2]:
import math

# Variables :
p = 5.;			#kg/cm**2
print ("Gauge units : ");

# Calculations and Results
print "Pressure Intensity in kg/m**2 : ",(p/10**-4)
g = 9.81;			#gravity consmath.tant
print "Pressure Intensity in N/m**2 : ",(p*g/10**-4)
print "Pressure Intensity in Pa : ",(p*g/10**-4)
print "Pressure Intensity in kPa : ",p*g/10**3/10**-4
print "Pressure Intensity in MPa : ",p*g/10**6/10**-4
print ("In terms of head : ");
w = 1000.;			#kg/m**3 for water
h = p*10**4/w;			#meter of water
print "Pressure is  : ",(h)," meter of water."
w = 13.6*1000;			#kg/m**3 for mercury
h = p*10**4/w;			#meter of mercury
print "Pressure is  : ",(h)," meter of mercury."
print ("Absolute units : ");
Patm = 760.;			#mm of mercury
Patm = 760*13.6/1000;			#m of water
Patm = Patm*1000.;			#kg/m**2
Pabs = p+Patm;			#kg/m**2
print "Absolute pressure in kg/m**2 : ",Pabs
print "Absolute pressure in kg/cm**2 : ",Pabs*10**4
print "Absolute pressure in N/m**2 : ",Pabs*10**4*g
print "Absolute pressure in Pa : ",Pabs*10**4*g
print "Absolute pressure in kPa : ",Pabs*10**5/10**3
print "Absolute pressure in MPa : ",Pabs*10**5/10**6
h1 = p*10.**4/w;			#meter of water
h2 = p*10.**4/1000;			#meter of water
h = h1+h2;			#			#meter of water
print "Absolute pressure head in terms of water in meter : ",h
w = 13.6*1000;			#kg/m**3 for mercury
h = p*10**4/w+760./1000;			#meter of mercury
print "Absolute pressure head in terms of mercury in meter : %.3f"%h

# note : rounding off error

Gauge units :
Pressure Intensity in kg/m**2 :  50000.0
Pressure Intensity in N/m**2 :  490500.0
Pressure Intensity in Pa :  490500.0
Pressure Intensity in kPa :  490.5
Pressure Intensity in MPa :  0.4905
Pressure is  :  50.0  meter of water.
Pressure is  :  3.67647058824  meter of mercury.
Absolute units :
Absolute pressure in kg/m**2 :  10341.0
Absolute pressure in kg/cm**2 :  103410000.0
Absolute pressure in N/m**2 :  1014452100.0
Absolute pressure in Pa :  1014452100.0
Absolute pressure in kPa :  1034100.0
Absolute pressure in MPa :  1034.1
Absolute pressure head in terms of water in meter :  53.6764705882
Absolute pressure head in terms of mercury in meter : 4.436


## Example 4.2 Page No : 88¶

In [3]:
import math

# Variables :
w = 1000.;			#kg/m**3
h = 50./1000;			#m

# Calculations and Results
p = w*h;			#kg/m**2
p = p*9.81;			#N/m**2 or Pa
print "Pressure Intensity in Pa : ",p
alfa = 30.;			#degree
h = 50;			#mm
print "Reading in tube in mm : ",l

Pressure Intensity in Pa :  490.5
Reading in tube in mm :  100.0


## Example 4.3 Page No : 89¶

In [3]:
import math

# Variables :
S1 = 13.6;			#sp. gravity of mercury
S2 = 1.;			#sp. gravity of water
H1 = 5.;			#m

# Calculations and Results
H2 = S1*H1/S2;			#m
print "(i) Pressure is ",(H2)," meter of water."

S2 = 0.79;			#sp. gravity of kerpsene
H1 = 5;			#m
H2 = S1*H1/S2;			#m
print "(ii) Pressure is ",round(H2,3)," meter of kerosene."

S2 = 1.7;			#sp. gravity of fluid
H1 = 5;			#m
H2 = S1*H1/S2;			#m
print "(iii) Pressure is ",(H2)," meter of fluid."

(i) Pressure is  68.0  meter of water.
(ii) Pressure is  86.076  meter of kerosene.
(iii) Pressure is  40.0  meter of fluid.


## Example 4.4 Page No : 95¶

In [4]:

# Variables :
S = 0.9;			#sp. gravity of liquid
Sm = 13.6;			#sp. gravity of mercury
S1 = Sm/S;			#sp. gravity

# Calculations
w = S*9.81;			#kN/m**3
h2 = 500./1000;			#m
h1 = 300./1000;			#m
a_BY_A = 1./80;			#ratio of area
pa = w*(h2*((S1-1)*a_BY_A+S1)-h1);			#kPa

# Results
print "Pressure in the pipe in kPa: %.3f"%pa

Pressure in the pipe in kPa: 64.838


## Example 4.5 Page No : 96¶

In [5]:
import math

# Variables :
S1 = 1.2;			#sp. gravity
S2 = 13.6;			#sp. gravity
w = 1000.;			#kg/m**3

# Calculations
h2 = 50./1000;			#m
h1 = 200./1000;			#m
pa = w*(S2*h1-S1*h2);			#kg/m**2

# Results
print "Pressure in the pipe in kg/m**2: ",pa
print "Pressure in the pipe in Pa: ",pa*9.81

Pressure in the pipe in kg/m**2:  2660.0
Pressure in the pipe in Pa:  26094.6


## Example 4.6 Page No : 97¶

In [6]:

# Variables :
S = 1.;			#sp. gravity
w = 1000.;			#kg/m**3
h2 = 50./1000;			#m
h1 = 200./1000;			#m

# Calculations
pa = w*S*(h1-h2);			#kg/m**2

# Results
print "Pressure in the pipe in kg/m**2: ",pa
print "Pressure in the pipe in Pa: ",pa*9.81

Pressure in the pipe in kg/m**2:  150.0
Pressure in the pipe in Pa:  1471.5


## Example 4.7 Page No : 97¶

In [7]:
import math

# Variables :
S1 = 0.005;			#sp. gravity
S2 = 1.;			#sp. gravity
Patm = 1.014*10**5;			#Pa
h = 50./1000;			#m
w = 1000.;			#kg/m**3

# Calculations
pa = -w*S2*h;			#kg/m**2
Pabs = pa*9.81+Patm;			#

# Results
print "Pressure intensity of gas in Pa(Vaccum): ",abs(pa*9.81)
print "Absolute pressure in the pipe in Pa: ",Pabs

Pressure intensity of gas in Pa(Vaccum):  490.5
Absolute pressure in the pipe in Pa:  100909.5


## Example 4.8 Page No : 100¶

In [8]:

# Variables :
S1 = 0.9;			#sp. gravity
S2 = 13.6;			#sp. gravity
h1 = 12.5/100;			#m

# Calculations and Results
P_AB = h1*(S2-S1);			#meter of water
print "Difference in pressure head at the points A & B is ",(P_AB)," meter of water"

w = 1000;			#kg/m**3
P_diff = P_AB*w*9.81;			#Pa or Nm**2
print "In terms A pressure entirely, the difference of pressure in N/m**2 : ",P_diff

Difference in pressure head at the points A & B is  1.5875  meter of water
In terms A pressure entirely, the difference of pressure in N/m**2 :  15573.375


## Example 4.9 Page No : 100¶

In [9]:

# Variables :
S1 = 1.;			#sp. gravity
S2 = 13.6;			#sp. gravity
h1 = 120./1000;			#m

# Calculations and Results
P_diff = h1*(S2-S1);			#meter of water
print "Difference in pressure head is ",(P_diff)," meter of water"
w = 1000;			#kg/m**3
P_diff = P_diff*w*9.81;			#Pa or Nm**2
print "In terms of pressure intensity, the difference of pressure in N/m**2 : ",P_diff

Difference in pressure head is  1.512  meter of water
In terms of pressure intensity, the difference of pressure in N/m**2 :  14832.72


## Example 4.10 Page No : 103¶

In [10]:
import math

# Variables :
S1 = 0.81;			#sp. gravity
S2 = 1.2;			#sp. gravity
S3 = 13.6;			#sp. gravity
h3 = 200./1000;			#m
h2 = 50./1000;			#m
h1 = 100./1000;			#m
w = 1000.;			#kg/m**3

# Calculations
pAB = ((h1*(S2-S1)+h2*(S3-S1)-h3*S1))*w;			#Kg/m**2

# Results
print "Pressure difference between the two vessel in kg/m**2: ",pAB

Pressure difference between the two vessel in kg/m**2:  516.5


## Example 4.11 Page No : 104¶

In [11]:
import math

# Variables :
S1 = 1.9;			#sp. gravity
S2 = 1.2;			#sp. gravity
S3 = 0.79;			#sp. gravity
h2 = 545./1000;			#m
h1 = 750./1000;			#m
h3 = h1-h2;			#m
w = 1000*9.81;			#N/m**3

# Calculations
pAB = (h1*S1-h2*S2-h3*S3)*w;			#N/m**2

# Results
print "Pressure difference between the two vessel in N/m**2: ",pAB

Pressure difference between the two vessel in N/m**2:  5974.7805


## Example 4.12 Page No : 105¶

In [12]:

# Variables :
S1 = 0.005;			#sp. gravity
S2 = 0.79;			#sp. gravity
S3 = 13.6;			#sp. gravity
h = 30./1000;			#m
w = 1000*9.81;			#N/m**3

# Calculations
pAB = h*(S3-S2)*w;			#N/m**2

# Results
print "Pressure difference between the two vessel in N/m**2: ",pAB

Pressure difference between the two vessel in N/m**2:  3769.983


## Example 4.13 Page No : 105¶

In [14]:
import math

# Variables :
S1 = 1.25;			#sp. gravity
S2 = 1.05;			#sp. gravity
S3 = 0.79;			#sp. gravity
h = 30./1000;			#m
w = 1000.;			#kg/m**3

# Calculations
#pA = pB
h = (0.15*w*S2-S1*w*0.15)/(S3*w-w*S2);			#m
h = h*1000;			#mm

# Results
print "Reading of manometer in mm : %.f"%h

Reading of manometer in mm : 115


## Example 4.14 Page No : 106¶

In [15]:
import math

# Variables :
S1 = 1.;			#sp. gravity of water
S2 = 1.;			#sp. gravity of water
S3 = 0.9;			#sp. gravity of oil
h3 = 100./1000;			#meter
w = 9.81*1000;			#N/m**3

# Calculations
pAB = w*(h3-h3*S3);			#N/m**2

# Results
print "Difference of pressure in N/m**2 or Pa : ",pAB

Difference of pressure in N/m**2 or Pa :  98.1