Respuesta :

Answer:

3.115× [tex]10^{-3}[/tex] meter

Explanation:

hall-petch constant for copper is given by

      [tex]S_0[/tex]=25 MPa

      k=0.12 for copper

now according to hall-petch equation

[tex]S_Y[/tex]=[tex]S_0[/tex] +[tex]\frac{K}{\sqrt{D}}[/tex]

240=25+[tex]\frac{0.12}{\sqrt{D}}[/tex]

D=3.115× [tex]10^{-3}[/tex] meter

so the grain diameter using the hall-petch equation=3.115×  [tex]10^{-3}[/tex] meter