Examples 1 -- Unit Conversion

In [1]:
from numpy import *
In [2]:
m_per_in = 0.0254       # converts inches to meters (exact)
m_per_ft = m_per_in*12  # converts ft to meters (exact)
km_per_mi = 1.609       # converts miles to kilometers
N_per_lb = 4.448        # converts pounds to Newtons
kN_per_kip = 4.448      # converts kips to kiloNewtons
kg_per_slug = 14.59     # converts slugs to kg
s_per_hr = 3600.        # converts hours to seconds
dtr = pi/180.           # converts degrees to radians

A. perform unit conversions

In [3]:
l = 2.22  # in
l * m_per_in
Out[3]:
0.056388
In [4]:
m = 0.278  # slug
m * kg_per_slug
Out[4]:
4.05602
In [5]:
F = 120  # lb
F * N_per_lb
Out[5]:
533.76
In [6]:
M = 30.6  # ft.lb
M * N_per_lb * m_per_ft
Out[6]:
41.485962240000006

B. more unit conversions

In [7]:
l = 121e-9 # m
l / m_per_in
Out[7]:
4.763779527559056e-06
In [8]:
m = 3.45  # kg = N s^2 / m
m2 = m / N_per_lb * m_per_in
print ('m = {:.3e} lb s^2/in'.format(m2))

m = 1.970e-02 lb s^2/in
In [9]:
F = 13.2e3   # N
F / N_per_lb
Out[9]:
2967.625899280575
In [10]:
I = 94.1  # kg m^2
I2 = I / kg_per_slug / m_per_in**2
print ('I = {:.3e} slug in^2'.format(I2))

I = 9.997e+03 slug in^2

C. density calculations with unit conversion

In [12]:
g = 9.81       # N/kg
rho = 7.365e3  # kg / m^3
print (rho / kg_per_slug * m_per_ft**3)
print (rho*g / N_per_lb  * m_per_ft**3)

14.294282052781353
459.9619092226359
In [13]:
rho = 3.90e3    # kg / m^3
print (rho / kg_per_slug * m_per_ft**3)
print (rho*g / N_per_lb  * m_per_ft**3)

7.569273592104178
243.56435111585603
In [14]:
rho = 960.    # kg / m^3
print (rho / kg_per_slug * m_per_ft**3)
print (rho*g / N_per_lb  * m_per_ft**3)

1.8632058072871824
59.954301813133796
In [15]:
rho = 0.8e3    # kg / m^3
print (rho / kg_per_slug * m_per_ft**3)
print (rho*g / N_per_lb  * m_per_ft**3)

1.552671506072652
49.961918177611494
In [ ]: