import math
#Variable declaration
l=0.16*10**-9 #bond distance
St=2.6*10**6 #cohesive strength
psi=6894.76
E=9*10**10 #Young modulus of silica
C=10**-8
#Calculation
Yp=4*l*St**2/E
Sf=math.sqrt((2*E*Yp)/(math.pi*C)) #Fracture stress for elliptical crack
Str=Sf/E #Strain
#Result
print'Fracture stress for elliptical crack = %.2f x 10^5 psi'%(Sf*10**-5)
print'Strain in percentage = %d percent'%(Str*6894.76*100)